Clinicopathological, Prognostic, and Molecular Differences Between Microsatellite-Stable Colorectal Cancer Patients Aged ≤ 30 Years and >30 Years

Clinicopathological, Prognostic, and Molecular Differences Between Microsatellite-Stable Colorectal Cancer Patients Aged ≤ 30 Years and >30 Years | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Clinicopathological, Prognostic, and Molecular Differences Between Microsatellite-Stable Colorectal Cancer Patients Aged ≤ 30 Years and >30 Years Yuanyuan Wang, Yi Jing, Yidi Yang, Bing Zhang, Zhu Chang, Yawen Wang, and 2 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8390621/v1 This work is licensed under a CC BY 4.0 License Status: Under Revision Version 1 posted 11 You are reading this latest preprint version Abstract Background The biological and clinical heterogeneity of younger patients with microsatellite stable (MSS)/proficient mismatch repair (pMMR) colorectal cancer (CRC) is largely unexplored. This retrospective study compared the clinicopathological factors, prognosis, and molecular characteristics of MSS/pMMR CRC in patients younger and older than 30 years. Methods Overall, 191 and 573 younger (≤ 30 years old) and older (> 30 years old) CRC patients, respectively, were enrolled. Statistically significant differences between the groups were determined using the χ 2 or Fisher's exact test. Progression-free survival (PFS) was assessed by Kaplan-Meier analysis and compared using log-rank test. Results Younger patients with MSS/pMMR CRC exhibited significantly more aggressive features, including higher rates of mucinous adenocarcinoma, poor differentiation, deeper tumour invasion and advanced tumour–node–metastasis (TNM) stage than older patients. Molecular analysis revealed a higher microsatellite instability-high (MSI-H) incidence but lower KRAS mutation frequency in younger patients compared to older individuals. Furthermore, comprehensive genetic profiling of 1021 genes revealed no additional significant variations and no significant differences in PFS between the two MSS/pMMR CRC groups. Conclusion Younger patients with CRC exhibit unique biological behaviour. Therefore, unravelling the mechanisms of its aggressiveness through integrated multi-omics technologies should be a key focus in future research. colorectal cancer ≤30 years microsatellite instability MSS Figures Figure 1 Figure 2 Introduction Colorectal cancer (CRC) is a leading cause of cancer-related mortality globally [ 1 ]. Recent studies [ 2 , 3 ] have shown that the incidence of CRC is age-related and has gradually shifted toward younger populations. Specifically, in early-onset CRC, increases were observed in the 20–29 and 30–39 age groups, with a more pronounced rise in the younger group [ 20 – 29 ] [ 4 ]. Microsatellite instability (MSI) is an important molecular biomarker of CRC and is classified as microsatellite instability-high (MSI-H), microsatellite instability-low (MSI-L), or microsatellite stable (MSS). MSI-H is caused by defects in the DNA mismatch repair (MMR) system, and is categorised as deficient mismatch repair (dMMR) or proficient mismatch repair (pMMR). Importantly, MSI-H and dMMR are clinically equivalent. Patients with MSI-H/dMMR CRC have demonstrated significant clinical benefits from immunotherapy [ 5 ]. Nonetheless, the MSI-H/dMMR phenotype is observed in a small subset (15%) of CRC cases, whereas most (85%) exhibit MSS/pMMR features [ 6 ]. CRC with MSS/pMMR is characterized by an immunologically “cold” tumor microenvironment and a lack of reliable biomarkers to guide combination immunotherapy. While previous studies on age disparities in CRC have largely focused on early-onset disease (≤ 50 years) or MSI-H/dMMR subtypes, the specific clinicopathological and molecular features of very young patients (≤ 30 years) with MSS/pMMR CRC remain unclear. To address this, we analyze a cohort of early-onset CRC patients (≤ 30 years) to delineate their unique characteristics, with the goal of informing more precise and stratified treatment strategies. Materials and methods Patient demographics and clinicopathological features This was a retrospective study of patients with CRC diagnosed and treated at Henan Cancer Hospital. Overall, 191 younger patients with CRC (≤ 30 years old) were enrolled from January 2015 to April 2025 after surgery (age, 13–30 years; mean, 27 years; median, 28 years). Additionally, 573 older adult patients with CRC (> 30 years) were recruited as controls in 2016 (age: 31–90 years; mean: 60 years; median: 60 years). The inclusion criteria were as follows: (1) initial CRC diagnosis and surgery at our hospital because of primary tumours; (2) pathologically confirmed CRC; and (3) staging according to the 8th pathologic TNM system recommended by the American Joint Committee on Cancer [ 7 ]. The exclusion criteria comprised the following: (1) familial adenomatous polyposis and (2) postoperative specimens with confirmed tumours in situ. Integration of Clinically Derived MSI, KRAS, and Multi-gene Sequencing Data in CRC This study systematically compiled and analysed three distinct clinical molecular testing datasets from patients with CRC: MSI status in 616 cases, ascertained through immunohistochemistry, polymerase chain reaction (PCR), and next-generation sequencing (NGS) by certified clinical laboratories; KRAS mutation profiles from 576 patients, with testing performed via real-time PCR, amplification refractory mutation system PCR, and NGS; and high-throughput sequencing data encompassing 1,021 genes from 30 MSS/pMMR CRC cases. All molecular testing procedures were originally conducted by accredited clinical laboratories, and this study focused exclusively on the retrospective analysis of these clinically generated datasets. Patient Follow-up and Survival Data Collection Clinical follow-up information for patients with CRC was obtained via telephone calls and review of electronic medical records, from the surgery date until April 2025. For follow-up, progression-free survival (PFS) was defined as the interval from surgery to tumour progression (including tumour recurrence, new metastasis, or death). PFS ranged from 1 to 78 months; complete survival data were available for 492 patients, and 272 were lost to follow-up. Statistical analysis All statistical analyses were performed using SPSS software (version 23.0; IBM Corp.). Statistically significant differences between the younger and older CRC groups were determined using the χ 2 or Fisher's exact test. PFS was estimated using the Kaplan–Meier method. Survival rates were calculated using log-rank tests. The RStudio software (version 4.3.2) was used to plot the genetic variation map. Differences were considered significant when P < 0.05. Results CRC Age Distribution Characteristics In 2016, 589 patients were diagnosed with CRC (age, 14–90 years; mean, 58 years; median, 59 years). Figure 1 displays the CRC distribution at different ages. In 2016, 16 patients with CRC were ≤ 30 years of age, accounting for 2.71% of all cases. The largest number of individuals with CRC (approximately 178 cases, 30.22%) was in the 60–70 age group. Regardless of MSI status, when segmented by 5-year age intervals, patients aged ≤ 30 exhibited the highest proportion in the 26–30 years age group (Table 1 ). Table 1 Age Distribution of CRC Patients Aged ≤ 30 Years by MSI Status ≤ 30 years total MSI-H/dMMR MSS /pMMR ≤ 15 3(1.57%) 2(4.08%) 1(0.82%) 16–20 15(7.85%) 5(10.20%) 10(8.20%) 21–25 35(18.33) 8(16.33%) 23(18.85%) 26–30 138(72.25%) 34(69.39%) 88(72.13%) total 191 49 122 Clinicopathological Features, MSI Status, and KRAS Mutations in Colorectal Cancer Patients Aged ≤ 30 Years Supplementary Table 1 presents the comparison of the clinicopathological features between the two groups. Younger patients showed a significant correlation with histology (χ 2 = 19.782, P < 0.001), tumour differentiation (χ 2 = 35.324, P < 0.001), invasion depth (χ 2 = 10.789, P = 0.001), vessel carcinoma embolus (χ 2 = 10.322, P = 0.001), lymph node metastasis (χ 2 = 10.810, P = 0.001), distant metastasis (χ 2 = 5.486, P = 0.019), and tumour–node–metastasis (TNM) stage (χ 2 = 17.583, P = 0.001). No significant correlation was observed between age and sex. MSI incidence was significantly higher in younger patients with CRC (28.65%) than in older ones (12.81%, χ 2 = 21.772, P 30 years (38.12%, χ 2 = 3.910, P < 0.048, Supplementary Table 2). Clinicopathological Characteristics and KRAS Mutations of MSS/pMMR CRC in Patients Aged ≤ 30 Years Table 2 compares the clinicopathological features of MSS/pMMR CRC between the younger and older groups. Among patients with MSS/pMMR CRC, compared to the > 30-year-old group, those aged ≤ 30 years exhibited significantly higher proportions of the following characteristics: mucinous adenocarcinoma (χ 2 = 9.613, P = 0.002), poor differentiation (χ 2 = 29.586, P < 0.001), deeper tumour invasion (T3/T4) (χ 2 = 10.282, P = 0.001), vessel carcinoma embolus (χ 2 = 13.943, P < 0.001), lymph node metastasis (χ 2 = 13.378, P < 0.001), distant metastasis (χ 2 = 7.509, P = 0.006), and advanced TNM stage (III-IV) (χ 2 = 20.037, P 30y (%) χ 2 value P value Gender 0.597 0.440 Male 283 64(52.5) 219(56.4) Female 227 58(47.5) 169(43.6) Histology 9.613 0.002 Adenocarcinoma 430 92(75.4) 338(87.1) Mucinous adenocarcinoma 80 30(24.6) 50(12.9) Tumor differentiation 29.586 <0.001 Moderate/well 373 66(54.1) 307(79.1) Poor 137 56(45.9) 81(20.9) Depth of invasion 10.282 0.001 T1/T2 75 7(5.7) 68(17.5) T3/T4 435 115(94.3) 320(82.5) Vessel carcinoma embolus 13.943 <0.001 Yes 176 25(20.5) 151(38.9) No 334 97(79.5) 237(61.1) Lymph node metastasis 13.378 <0.001 Yes 240 75(61.5) 165(42.5) No 270 47(38.5) 223(57.5) Distant metastasis 7.509 0.006 Yes 74 27(22.1) 47(12.1) No 436 95(77.9) 341(87.9) TNM stage 20.037 <0.001 I 54 2(1.6) 52(13.4) II 195 40(32.8) 155(39.9) III 195 61(50.0) 134(34.5) IV 66 19(15.6) 47(12.1) Among patients with MSS/pMMR CRC, KRAS mutation testing was performed in 425 cases, with a mutation rate of 31.53% (134/425). A significantly lower KRAS mutation rate was observed in younger than in older patients with MSS/pMMR CRC (18.7%, 20/107) (35.8%,114/318) (χ 2 = 10.917, P = 0.001). Landscape of Genetic Variations in Young CRC Patients High-throughput sequencing data of 1,021 genes were collected from 30 patients with MSS/pMMR CRC, including nine and 21 individuals aged ≤ 30 and > 30 years, respectively, as shown in Fig. 2 . The five most frequently altered genes were TP53 (76.7%, 23/30), APC (66.7%, 20/30), KRAS (53.3%, 16/30), LRP1B (23.3%, 7/30), and FBXW7 (23.3%, 7/30). All genes with an alteration frequency exceeding 10% showed no significant difference in their variant rates between the two patient groups, as determined by Fisher's exact test. PFS Data in CRC In the younger patients with CRC, disease progression, stable disease, and follow-up loss occurred in 38, 101, and 52 cases, respectively. The PFS in this group ranged from 1 to 78 months, with a median of 26 months; the disease progression rate was 27.34%. In the > 30-year-old group, 120, 233, and 220 patients experienced disease progression, achieved stable disease, and were lost to follow-up, respectively. The PFS in this group ranged from 2 to 65 months, with a median of 48 months; the PFS rate was 33.99%. No significant difference in PFS was observed between the two groups (log-rank χ 2 = 0.971, P = 0.324). Among the 92 individuals with MSS/pMMR CRC aged ≤ 30 years, 32 experienced disease progression. This subgroup exhibited a PFS ranging from 14 to 30 months (median, 27 months), with a disease progression rate of 34.78%. Progression events occurred in 92/247 MSS/pMMR patients (> 30 years old), and the PFS spanned from 2 to 65 months (median, 48 months), yielding a PFS rate of 37.24%. There was no significant difference in PFS (log-rank χ 2 = 2.644, P = 0.104) between these two MSS/pMMR CRC groups. Discussion Previous studies on younger patients have mainly focused on those aged < 50 years [ 8 – 10 ]. Globally [ 11 ], the rising incidence of CRC among adolescents and young adults has been consistently documented across multiple countries, including Japan and the United Kingdom [ 12 ] [ 13 ]. Despite representing only 2.7% of CRC cases, younger patients (≤ 30 years) typically demonstrate superior physical condition, better adherence to therapy, and a more intense survival drive, warranting greater focus owing to their heightened socioeconomic impact. In the current study, all patients aged ≤ 30 years with CRC or MSS/pMMR CRC demonstrated the same distinct clinicopathological features as those aged > 30 years. Younger patients exhibited significantly higher proportions of mucinous adenocarcinoma, poor differentiation, deep tumour invasion (T3/T4), vascular tumour emboli, lymph node metastasis, distant metastasis, and advanced TNM stage (III-IV) compared to older individuals, indicating more aggressive clinicopathological features in the former group. While the age cut-off values for defining young cohorts vary across studies, all investigations have consistently demonstrated that younger patients tend to present with more aggressive clinicopathological features [ 12 , 14 , 15 ]. The increased proportion of mucinous adenocarcinoma and signet-ring cell carcinoma in patients with young-onset CRC currently lacks a definitive pathological explanation, necessitating future investigations using multi-omics approaches (including genomic, transcriptomic, and gut microbiome profiling) to elucidate the underlying mechanisms. In China, current guidelines recommend initiating CRC screening at the age of 50 years for asymptomatic average-risk individuals. Younger patients with CRC frequently present with advanced-stage disease at diagnosis, potentially due to inadequate screening participation and/or nonspecific clinical manifestations. Similar to the findings of prior studies [ 16 – 18 ] the MSI-H/dMMR rate was elevated in the younger cohort (28.65% vs. 12.81%), with MSS/pMMR accounting for most cases (71.35%). Subsequently, we sought to explore potential differences in the gene expression profiles between the two MSS/pMMR patient groups. Consistent with previous findings, TP53 , APC , and KRAS remained the most frequently mutated oncogenic drivers in both young and older CRC cohorts [ 19 ]. Following MSI, KRAS is the second most clinically significant molecular biomarker in CRC, with a mutation prevalence of 40–50%. Notably, patients with CRC carrying KRAS mutations in exons 2–4 demonstrate complete resistance to anti-epidermal growth factor receptor therapies. In line with observations in younger patients (≤ 40 years) [ 20 ], this study confirms that colorectal cancer patients aged ≤ 30 years with MSS status also exhibit a lower frequency of KRAS mutations. Currently, the fundamental mechanism underlying the more aggressive biological behavior of colorectal cancer in younger patients remains undetermined. Therefore, this study investigates the differences in gene expression profiles between the two age groups from a genetic perspective, aiming to identify potential molecular associations. Our extensive screening of 1021 genes demonstrated that, beyond KRAS , there were no other significant differences in the alternation frequencies between the younger and older MSS patient groups. This highlights that within a rigorously defined MSS population, the mutational landscape can appear remarkably stable. The research by Richarda et al. on MSS CRC demonstrated that adolescent patients (≤ 25 years) in their cohort exhibited significantly higher TP53 mutation rates yet lower APC mutation frequencies than did older adult patients (> 60 years) from The Cancer Genome Atlas database [ 15 ]. Furthermore, Lieu et al. recently reported a higher TP53 mutation rates and lower APC mutation frequency in MSS CRCs diagnosed before the age of 40 years than they did in those diagnosed over the age of 50 years [ 21 ]. Conversely, Salem et al. found a higher APC mutation frequency in a similar young-onset patient cohort [ 22 ]. Nonetheless, both the current study and another Asian report found no significant differences in TP53 mutation rates between the two patient groups [ 23 ]. These inconsistencies are likely attributable to considerable heterogeneity in study cohorts, including differences in age cut-offs, geographical and ethnic backgrounds, sample sizes, and the potential inclusion of undiagnosed hereditary syndromes. Previous research has reported conflicting outcomes between younger and older patients with CRC. If patients with CRC are younger than 40 or 50 [ 24 , 25 ] years of age, their prognosis improves when compared to that of older patients. This may be mainly due to their healthier baseline status and comorbidity absence. However, other studies have demonstrated that young-onset patients with CRC tend to present with more advanced disease at diagnosis, leading to worse outcomes and survival rates than those of older patients [ 26 – 28 ]. Owing to a general lack of awareness of CRC among younger individuals, early symptoms are often mistaken for poor diet or gastrointestinal disorders, delaying the optimal window for diagnosis and treatment. This delay may cause tumour progression to more severe conditions with deeper infiltration or metastasis, thereby increasing treatment difficulty and worsening the prognosis [ 20 ]. The present study revealed no significant prognosis difference between the two age groups. Previous research indicated that younger patients could undergo more aggressive surgical and perioperative treatments, potentially explaining the similar outcomes between age groups [ 29 , 30 ]. Conclusion In conclusion, our study delineates a distinct profile for young MSS colorectal cancer patients, characterized by aggressive clinicopathological features and a uniquely lower KRAS mutation frequency. The key finding—the absence of other significant genomic differences across a 1021-gene panel—strongly suggests that the aggressive phenotype in these young patients is not driven by a higher burden of somatic mutations in common cancer genes. Instead, their aggressive clinical behaviour may involve alternative mechanisms. The primary limitation of this work is its limited cohort size, necessitating validation in larger, multi-centre studies. Future research should prioritize integrated multi-omics approaches to unravel the drivers of this clinically challenging entity. Abbreviations CRC Colorectal Cancer MMR Mismatch Repair pMMR Proficient Mismatch Repair dMMR Deficient Mismatch Repair MSI Microsatellite Instability MSI-H Microsatellite Instability-High MSI-L Microsatellite Instability-Low MSS Microsatellite Stable TNM Tumour–Node–Metastasis PFS Progression-Free Survival PCR Polymerase Chain Reaction NGS Next-Generation Sequencing Declarations Ethics approval and consent to participate This retrospective cohort study was reviewed and approved by the Institutional Ethics Committee of the Affiliated Cancer Hospital of Zhengzhou University (No.2022-318-001). The requirement for written informed consent was waived by the aforementioned ethics committee due to the retrospective nature of the study, which involved the analysis of anonymized existing data. All procedures performed in studies involving human participants were in accordance with the ethical standards of institutional and/or national research committees, as well as with the 1964 Helsinki declaration and its later amendments. Consent for publication This study contains no personally identifiable data. Approval for publication was obtained from all authors. Competing interests We declare no competing interests. Funding This study was supported by the Henan Province Medical Science and Technology Research Program [Grant No.: LHGJ20250196]. Author Contribution Q.X. conceived and designed the study. B.Z., C.Z., Y.W. and Y.Z. collected the clinical data and conducted telephone follow-ups. Y.J. performed the statistical analysis. Y.W. (Yuanyuan Wang) wrote the main manuscript text. 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Supplementary Table 2 Comparison of MSI and KRAS Mutation Data Between the Two Age Groups with CRC Cite Share Download PDF Status: Under Revision Version 1 posted Editorial decision: Revision requested 09 Mar, 2026 Reviews received at journal 09 Mar, 2026 Reviews received at journal 01 Mar, 2026 Reviewers agreed at journal 12 Feb, 2026 Reviewers agreed at journal 10 Feb, 2026 Reviewers agreed at journal 05 Feb, 2026 Reviewers invited by journal 23 Jan, 2026 Editor invited by journal 13 Jan, 2026 Editor assigned by journal 02 Jan, 2026 Submission checks completed at journal 30 Dec, 2025 First submitted to journal 30 Dec, 2025 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-8390621","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":580949344,"identity":"b5f03910-e75d-4e6e-b031-e089f5f5fd73","order_by":0,"name":"Yuanyuan Wang","email":"","orcid":"","institution":"The Affiliated Cancer Hospital of Zhengzhou University \u0026 Henan Cancer Hospital","correspondingAuthor":false,"prefix":"","firstName":"Yuanyuan","middleName":"","lastName":"Wang","suffix":""},{"id":580949345,"identity":"293c4048-3100-4a59-8e6a-1389568927c0","order_by":1,"name":"Yi Jing","email":"","orcid":"","institution":"The Affiliated Cancer Hospital of Zhengzhou University \u0026 Henan Cancer Hospital","correspondingAuthor":false,"prefix":"","firstName":"Yi","middleName":"","lastName":"Jing","suffix":""},{"id":580949346,"identity":"9622186b-1d58-4c2d-afd5-3acccea6f82b","order_by":2,"name":"Yidi Yang","email":"","orcid":"","institution":"The Affiliated Cancer Hospital of Zhengzhou University \u0026 Henan Cancer Hospital","correspondingAuthor":false,"prefix":"","firstName":"Yidi","middleName":"","lastName":"Yang","suffix":""},{"id":580949347,"identity":"c470820f-556a-4efa-9585-5f9742267fb7","order_by":3,"name":"Bing Zhang","email":"","orcid":"","institution":"The Affiliated Cancer Hospital of Zhengzhou University \u0026 Henan Cancer Hospital","correspondingAuthor":false,"prefix":"","firstName":"Bing","middleName":"","lastName":"Zhang","suffix":""},{"id":580949348,"identity":"564709a4-41f1-432d-ae6a-c68db8d664e3","order_by":4,"name":"Zhu Chang","email":"","orcid":"","institution":"The Affiliated Cancer Hospital of Zhengzhou University \u0026 Henan Cancer Hospital","correspondingAuthor":false,"prefix":"","firstName":"Zhu","middleName":"","lastName":"Chang","suffix":""},{"id":580949349,"identity":"5a407838-d3b8-4d71-87f9-2e4c97bd0e29","order_by":5,"name":"Yawen Wang","email":"","orcid":"","institution":"the Fifth Affiliated Hospital of Zhengzhou University","correspondingAuthor":false,"prefix":"","firstName":"Yawen","middleName":"","lastName":"Wang","suffix":""},{"id":580949350,"identity":"a525ef8b-3dcf-490c-84f5-fa1f9500812a","order_by":6,"name":"Yinping Zhang","email":"","orcid":"","institution":"The Affiliated Cancer Hospital of Zhengzhou University \u0026 Henan Cancer Hospital","correspondingAuthor":false,"prefix":"","firstName":"Yinping","middleName":"","lastName":"Zhang","suffix":""},{"id":580949351,"identity":"2a7d98d6-0c7e-4b09-93f7-95b5e3bb98dd","order_by":7,"name":"Qingxin Xia","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA+ElEQVRIiWNgGAWjYHACAwYGHglmNv7+BwYJPDY8/PwN+NXzgLXIWLDzSZxhKPggkyYjOeMAMVpsKvjlGHIYPs6wOWxj0JCAX4u9RPLGxzw5EtJsDGcPbubJOc9jwHCA8cPHHDy2SKQVG/OckTBmY+5LBjJu85gzNzBLztyGT0uOmTRvj0QyG8MBM2Pents8lg0H2Jh5CWr5J1HfxpBg/pv33zkegwMJRGjhAQUyQ46B4QyeA0RoOfOs2HAOSIvEsQSDDzzJPJIzDjbj9Qt7e/LGB2946pjl+5sPAKPSzp6fv/ngh494tGADjA2kqR8Fo2AUjIJRgAEAtBhIwDEvvjIAAAAASUVORK5CYII=","orcid":"","institution":"The Affiliated Cancer Hospital of Zhengzhou University \u0026 Henan Cancer Hospital","correspondingAuthor":true,"prefix":"","firstName":"Qingxin","middleName":"","lastName":"Xia","suffix":""}],"badges":[],"createdAt":"2025-12-18 03:39:19","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-8390621/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-8390621/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":101397966,"identity":"9459f048-7c70-457d-98ed-6368dc9d1559","added_by":"auto","created_at":"2026-01-29 09:38:29","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":55905,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eProportion of Colorectal Cancer Patients by Age Group.\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-8390621/v1/cdee4f3011a378b2c48b96a6.png"},{"id":101364435,"identity":"619d5dc4-3a80-469a-b1f1-2aaf99534b73","added_by":"auto","created_at":"2026-01-29 00:49:59","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":76418,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eHigh-throughput Sequencing Data of 1,021 Genes in 30 MSS/pMMR CRC Patients. \u003c/strong\u003eA shows the alteration frequency of all genes with an alteration rate greater than 10%. B displays the genetic alteration landscape across all patients. C presents the gene variant frequencies in the two patient groups.\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-8390621/v1/ec5d1e86a15ccb8131a1b34b.png"},{"id":101751299,"identity":"a4c38045-11e1-4cf6-af32-b5650d53607f","added_by":"auto","created_at":"2026-02-03 10:19:06","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":977761,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8390621/v1/5c234621-579c-4edb-a993-2a2387b7777c.pdf"},{"id":101364437,"identity":"8fd0074d-58a6-4216-90ed-7596ae791d78","added_by":"auto","created_at":"2026-01-29 00:49:59","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":22561,"visible":true,"origin":"","legend":"\u003cp\u003eSupplementary Table 1 Comparison of CRC Clinicopathological Data Between the Two Age Groups.\u003c/p\u003e\n\u003cp\u003eSupplementary Table 2 Comparison of MSI and \u003cem\u003eKRAS\u003c/em\u003eMutation Data Between the Two Age Groups with CRC\u003c/p\u003e","description":"","filename":"Supplementarymaterial.docx","url":"https://assets-eu.researchsquare.com/files/rs-8390621/v1/84664e53e4aa63307245e7ad.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"Clinicopathological, Prognostic, and Molecular Differences Between Microsatellite-Stable Colorectal Cancer Patients Aged ≤ 30 Years and \u003e30 Years","fulltext":[{"header":"Introduction","content":"\u003cp\u003eColorectal cancer (CRC) is a leading cause of cancer-related mortality globally [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. Recent studies [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e] have shown that the incidence of CRC is age-related and has gradually shifted toward younger populations. Specifically, in early-onset CRC, increases were observed in the 20\u0026ndash;29 and 30\u0026ndash;39 age groups, with a more pronounced rise in the younger group [\u003cspan additionalcitationids=\"CR21 CR22 CR23 CR24 CR25 CR26 CR27 CR28\" citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e] [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eMicrosatellite instability (MSI) is an important molecular biomarker of CRC and is classified as microsatellite instability-high (MSI-H), microsatellite instability-low (MSI-L), or microsatellite stable (MSS). MSI-H is caused by defects in the DNA mismatch repair (MMR) system, and is categorised as deficient mismatch repair (dMMR) or proficient mismatch repair (pMMR). Importantly, MSI-H and dMMR are clinically equivalent. Patients with MSI-H/dMMR CRC have demonstrated significant clinical benefits from immunotherapy [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. Nonetheless, the MSI-H/dMMR phenotype is observed in a small subset (15%) of CRC cases, whereas most (85%) exhibit MSS/pMMR features [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eCRC with MSS/pMMR is characterized by an immunologically \u0026ldquo;cold\u0026rdquo; tumor microenvironment and a lack of reliable biomarkers to guide combination immunotherapy. While previous studies on age disparities in CRC have largely focused on early-onset disease (\u0026le;\u0026thinsp;50 years) or MSI-H/dMMR subtypes, the specific clinicopathological and molecular features of very young patients (\u0026le;\u0026thinsp;30 years) with MSS/pMMR CRC remain unclear. To address this, we analyze a cohort of early-onset CRC patients (\u0026le;\u0026thinsp;30 years) to delineate their unique characteristics, with the goal of informing more precise and stratified treatment strategies.\u003c/p\u003e"},{"header":"Materials and methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003ePatient demographics and clinicopathological features\u003c/h2\u003e \u003cp\u003eThis was a retrospective study of patients with CRC diagnosed and treated at Henan Cancer Hospital. Overall, 191 younger patients with CRC (\u0026le;\u0026thinsp;30 years old) were enrolled from January 2015 to April 2025 after surgery (age, 13\u0026ndash;30 years; mean, 27 years; median, 28 years). Additionally, 573 older adult patients with CRC (\u0026gt;\u0026thinsp;30 years) were recruited as controls in 2016 (age: 31\u0026ndash;90 years; mean: 60 years; median: 60 years). The inclusion criteria were as follows: (1) initial CRC diagnosis and surgery at our hospital because of primary tumours; (2) pathologically confirmed CRC; and (3) staging according to the 8th pathologic TNM system recommended by the American Joint Committee on Cancer [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. The exclusion criteria comprised the following: (1) familial adenomatous polyposis and (2) postoperative specimens with confirmed tumours in situ.\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eIntegration of Clinically Derived MSI, KRAS, and Multi-gene Sequencing Data in CRC\u003c/h3\u003e\n\u003cp\u003eThis study systematically compiled and analysed three distinct clinical molecular testing datasets from patients with CRC: MSI status in 616 cases, ascertained through immunohistochemistry, polymerase chain reaction (PCR), and next-generation sequencing (NGS) by certified clinical laboratories; \u003cem\u003eKRAS\u003c/em\u003e mutation profiles from 576 patients, with testing performed via real-time PCR, amplification refractory mutation system PCR, and NGS; and high-throughput sequencing data encompassing 1,021 genes from 30 MSS/pMMR CRC cases. All molecular testing procedures were originally conducted by accredited clinical laboratories, and this study focused exclusively on the retrospective analysis of these clinically generated datasets.\u003c/p\u003e\n\u003ch3\u003ePatient Follow-up and Survival Data Collection\u003c/h3\u003e\n\u003cp\u003eClinical follow-up information for patients with CRC was obtained via telephone calls and review of electronic medical records, from the surgery date until April 2025. For follow-up, progression-free survival (PFS) was defined as the interval from surgery to tumour progression (including tumour recurrence, new metastasis, or death). PFS ranged from 1 to 78 months; complete survival data were available for 492 patients, and 272 were lost to follow-up.\u003c/p\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003eStatistical analysis\u003c/h2\u003e \u003cp\u003eAll statistical analyses were performed using SPSS software (version 23.0; IBM Corp.). Statistically significant differences between the younger and older CRC groups were determined using the \u003cem\u003eχ\u003c/em\u003e\u003csup\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sup\u003e or Fisher's exact test. PFS was estimated using the Kaplan\u0026ndash;Meier method. Survival rates were calculated using log-rank tests. The RStudio software (version 4.3.2) was used to plot the genetic variation map. Differences were considered significant when P\u0026thinsp;\u0026lt;\u0026thinsp;0.05.\u003c/p\u003e \u003c/div\u003e"},{"header":"Results","content":"\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003eCRC Age Distribution Characteristics\u003c/h2\u003e \u003cp\u003eIn 2016, 589 patients were diagnosed with CRC (age, 14\u0026ndash;90 years; mean, 58 years; median, 59 years). Figure\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e displays the CRC distribution at different ages. In 2016, 16 patients with CRC were \u0026le;\u0026thinsp;30 years of age, accounting for 2.71% of all cases. The largest number of individuals with CRC (approximately 178 cases, 30.22%) was in the 60\u0026ndash;70 age group. Regardless of MSI status, when segmented by 5-year age intervals, patients aged\u0026thinsp;\u0026le;\u0026thinsp;30 exhibited the highest proportion in the 26\u0026ndash;30 years age group (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eAge Distribution of CRC Patients Aged\u0026thinsp;\u0026le;\u0026thinsp;30 Years by MSI Status\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"4\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u0026le;\u0026thinsp;30 years total\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eMSI-H/dMMR\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eMSS /pMMR\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u0026le;\u0026thinsp;15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3(1.57%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2(4.08%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1(0.82%)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e16\u0026ndash;20\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e15(7.85%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e5(10.20%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e10(8.20%)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e21\u0026ndash;25\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e35(18.33)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e8(16.33%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e23(18.85%)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e26\u0026ndash;30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e138(72.25%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e34(69.39%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e88(72.13%)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003etotal\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e191\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e49\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e122\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003cb\u003eClinicopathological Features, MSI Status, and\u003c/b\u003e \u003cb\u003eKRAS\u003c/b\u003e \u003cb\u003eMutations in Colorectal Cancer Patients Aged\u0026thinsp;\u0026le;\u0026thinsp;30 Years\u003c/b\u003e\u003c/p\u003e \u003cp\u003eSupplementary Table\u0026nbsp;1 presents the comparison of the clinicopathological features between the two groups. Younger patients showed a significant correlation with histology (χ\u003csup\u003e2\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;19.782, P\u0026thinsp;\u0026lt;\u0026thinsp;0.001), tumour differentiation (χ\u003csup\u003e2\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;35.324, P\u0026thinsp;\u0026lt;\u0026thinsp;0.001), invasion depth (χ\u003csup\u003e2\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;10.789, P\u0026thinsp;=\u0026thinsp;0.001), vessel carcinoma embolus (χ\u003csup\u003e2\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;10.322, P\u0026thinsp;=\u0026thinsp;0.001), lymph node metastasis (χ\u003csup\u003e2\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;10.810, P\u0026thinsp;=\u0026thinsp;0.001), distant metastasis (χ\u003csup\u003e2\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;5.486, P\u0026thinsp;=\u0026thinsp;0.019), and tumour\u0026ndash;node\u0026ndash;metastasis (TNM) stage (χ\u003csup\u003e2\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;17.583, P\u0026thinsp;=\u0026thinsp;0.001). No significant correlation was observed between age and sex.\u003c/p\u003e \u003cp\u003eMSI incidence was significantly higher in younger patients with CRC (28.65%) than in older ones (12.81%, χ\u003csup\u003e2\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;21.772, P\u0026thinsp;\u0026lt;\u0026thinsp;0.001, Supplementary Table\u0026nbsp;2). The \u003cem\u003eKRAS\u003c/em\u003e mutation rate in younger patients was 29.14%, which was significantly lower than that in patients aged\u0026gt;30 years (38.12%, χ\u003csup\u003e2\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;3.910, P\u0026thinsp;\u0026lt;\u0026thinsp;0.048, Supplementary Table\u0026nbsp;2).\u003c/p\u003e \u003cp\u003e \u003cb\u003eClinicopathological Characteristics and\u003c/b\u003e \u003cb\u003eKRAS\u003c/b\u003e \u003cb\u003eMutations of MSS/pMMR CRC in Patients Aged\u0026thinsp;\u0026le;\u0026thinsp;30 Years\u003c/b\u003e\u003c/p\u003e \u003cp\u003eTable\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e compares the clinicopathological features of MSS/pMMR CRC between the younger and older groups. Among patients with MSS/pMMR CRC, compared to the \u0026gt;\u0026thinsp;30-year-old group, those aged\u0026thinsp;\u0026le;\u0026thinsp;30 years exhibited significantly higher proportions of the following characteristics: mucinous adenocarcinoma (χ\u003csup\u003e2\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;9.613, P\u0026thinsp;=\u0026thinsp;0.002), poor differentiation (χ\u003csup\u003e2\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;29.586, P \u0026lt; 0.001), deeper tumour invasion (T3/T4) (χ\u003csup\u003e2\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;10.282, P\u0026thinsp;=\u0026thinsp;0.001), vessel carcinoma embolus (χ\u003csup\u003e2\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;13.943, P \u0026lt; 0.001), lymph node metastasis (χ\u003csup\u003e2\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;13.378, P \u0026lt; 0.001), distant metastasis (χ\u003csup\u003e2\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;7.509, P\u0026thinsp;=\u0026thinsp;0.006), and advanced TNM stage (III-IV) (χ\u003csup\u003e2\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;20.037, P \u0026lt; 0.001).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eComparison of Clinicopathological Characteristics Between the Two Age Groups of Patients with MSS/pMMR CRC\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"9\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eVariable\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e \u003cp\u003eCases\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e \u003cp\u003e\u0026le;\u0026thinsp;30y (%)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u0026gt;30y (%)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c8\" namest=\"c7\"\u003e \u003cp\u003e\u003cem\u003eχ\u003c/em\u003e\u003csup\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sup\u003e value\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c9\"\u003e \u003cp\u003eP value\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eGender\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0.597\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c9\" namest=\"c8\"\u003e \u003cp\u003e0.440\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMale\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e283\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e \u003cp\u003e64(52.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e \u003cp\u003e219(56.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\" morerows=\"1\" rowspan=\"2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" morerows=\"1\" nameend=\"c9\" namest=\"c8\" rowspan=\"2\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eFemale\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e227\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e \u003cp\u003e58(47.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e \u003cp\u003e169(43.6)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHistology\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e9.613\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c9\" namest=\"c8\"\u003e \u003cp\u003e0.002\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAdenocarcinoma\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e430\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e \u003cp\u003e92(75.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e \u003cp\u003e338(87.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\" morerows=\"1\" rowspan=\"2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" morerows=\"1\" nameend=\"c9\" namest=\"c8\" rowspan=\"2\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMucinous adenocarcinoma\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e80\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e \u003cp\u003e30(24.6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e \u003cp\u003e50(12.9)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTumor differentiation\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e29.586\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c9\" namest=\"c8\"\u003e \u003cp\u003e\u0026lt;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eModerate/well\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e373\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e \u003cp\u003e66(54.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e \u003cp\u003e307(79.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c9\" namest=\"c8\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePoor\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e137\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e \u003cp\u003e56(45.9)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e \u003cp\u003e81(20.9)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c9\" namest=\"c8\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDepth of invasion\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e10.282\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c9\" namest=\"c8\"\u003e \u003cp\u003e0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eT1/T2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e75\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e \u003cp\u003e7(5.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e \u003cp\u003e68(17.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\" morerows=\"1\" rowspan=\"2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" morerows=\"1\" nameend=\"c9\" namest=\"c8\" rowspan=\"2\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eT3/T4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e435\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e \u003cp\u003e115(94.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e \u003cp\u003e320(82.5)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eVessel carcinoma embolus\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e13.943\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c9\" namest=\"c8\"\u003e \u003cp\u003e\u0026lt;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eYes\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e176\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e \u003cp\u003e25(20.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e \u003cp\u003e151(38.9)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c9\" namest=\"c8\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNo\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e334\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e \u003cp\u003e97(79.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e \u003cp\u003e237(61.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c9\" namest=\"c8\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLymph node metastasis\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e13.378\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c9\" namest=\"c8\"\u003e \u003cp\u003e\u0026lt;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eYes\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e240\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e \u003cp\u003e75(61.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e \u003cp\u003e165(42.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\" morerows=\"1\" rowspan=\"2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" morerows=\"1\" nameend=\"c9\" namest=\"c8\" rowspan=\"2\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNo\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e270\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e \u003cp\u003e47(38.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e \u003cp\u003e223(57.5)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDistant metastasis\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e7.509\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c9\" namest=\"c8\"\u003e \u003cp\u003e0.006\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eYes\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e74\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e \u003cp\u003e27(22.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e \u003cp\u003e47(12.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\" morerows=\"1\" rowspan=\"2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" morerows=\"1\" nameend=\"c9\" namest=\"c8\" rowspan=\"2\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNo\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e436\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e \u003cp\u003e95(77.9)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e \u003cp\u003e341(87.9)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTNM stage\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e20.037\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c9\" namest=\"c8\"\u003e \u003cp\u003e\u0026lt;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eI\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e54\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e \u003cp\u003e2(1.6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e \u003cp\u003e52(13.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\" morerows=\"3\" rowspan=\"4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" morerows=\"3\" nameend=\"c9\" namest=\"c8\" rowspan=\"4\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eII\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e195\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e \u003cp\u003e40(32.8)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e \u003cp\u003e155(39.9)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eIII\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e195\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e \u003cp\u003e61(50.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e \u003cp\u003e134(34.5)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eIV\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e66\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e \u003cp\u003e19(15.6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e \u003cp\u003e47(12.1)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eAmong patients with MSS/pMMR CRC, \u003cem\u003eKRAS\u003c/em\u003e mutation testing was performed in 425 cases, with a mutation rate of 31.53% (134/425). A significantly lower \u003cem\u003eKRAS\u003c/em\u003e mutation rate was observed in younger than in older patients with MSS/pMMR CRC (18.7%, 20/107) (35.8%,114/318) (χ\u003csup\u003e2\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;10.917, P\u0026thinsp;=\u0026thinsp;0.001).\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eLandscape of Genetic Variations in Young CRC Patients\u003c/h3\u003e\n\u003cp\u003eHigh-throughput sequencing data of 1,021 genes were collected from 30 patients with MSS/pMMR CRC, including nine and 21 individuals aged\u0026thinsp;\u0026le;\u0026thinsp;30 and \u0026gt;\u0026thinsp;30 years, respectively, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. The five most frequently altered genes were \u003cem\u003eTP53\u003c/em\u003e (76.7%, 23/30), APC (66.7%, 20/30), KRAS (53.3%, 16/30), LRP1B (23.3%, 7/30), and FBXW7 (23.3%, 7/30). All genes with an alteration frequency exceeding 10% showed no significant difference in their variant rates between the two patient groups, as determined by Fisher's exact test.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e\n\u003ch3\u003ePFS Data in CRC\u003c/h3\u003e\n\u003cp\u003eIn the younger patients with CRC, disease progression, stable disease, and follow-up loss occurred in 38, 101, and 52 cases, respectively. The PFS in this group ranged from 1 to 78 months, with a median of 26 months; the disease progression rate was 27.34%. In the \u0026gt;\u0026thinsp;30-year-old group, 120, 233, and 220 patients experienced disease progression, achieved stable disease, and were lost to follow-up, respectively. The PFS in this group ranged from 2 to 65 months, with a median of 48 months; the PFS rate was 33.99%. No significant difference in PFS was observed between the two groups (log-rank χ\u003csup\u003e2\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;0.971, P\u0026thinsp;=\u0026thinsp;0.324).\u003c/p\u003e \u003cp\u003eAmong the 92 individuals with MSS/pMMR CRC aged\u0026thinsp;\u0026le;\u0026thinsp;30 years, 32 experienced disease progression. This subgroup exhibited a PFS ranging from 14 to 30 months (median, 27 months), with a disease progression rate of 34.78%. Progression events occurred in 92/247 MSS/pMMR patients (\u0026gt;\u0026thinsp;30 years old), and the PFS spanned from 2 to 65 months (median, 48 months), yielding a PFS rate of 37.24%. There was no significant difference in PFS (log-rank χ\u003csup\u003e2\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;2.644, P\u0026thinsp;=\u0026thinsp;0.104) between these two MSS/pMMR CRC groups.\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003ePrevious studies on younger patients have mainly focused on those aged\u0026thinsp;\u0026lt;\u0026thinsp;50 years [\u003cspan additionalcitationids=\"CR9\" citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. Globally [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e], the rising incidence of CRC among adolescents and young adults has been consistently documented across multiple countries, including Japan and the United Kingdom [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e] [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. Despite representing only 2.7% of CRC cases, younger patients (\u0026le;\u0026thinsp;30 years) typically demonstrate superior physical condition, better adherence to therapy, and a more intense survival drive, warranting greater focus owing to their heightened socioeconomic impact.\u003c/p\u003e \u003cp\u003eIn the current study, all patients aged\u0026thinsp;\u0026le;\u0026thinsp;30 years with CRC or MSS/pMMR CRC demonstrated the same distinct clinicopathological features as those aged\u0026thinsp;\u0026gt;\u0026thinsp;30 years. Younger patients exhibited significantly higher proportions of mucinous adenocarcinoma, poor differentiation, deep tumour invasion (T3/T4), vascular tumour emboli, lymph node metastasis, distant metastasis, and advanced TNM stage (III-IV) compared to older individuals, indicating more aggressive clinicopathological features in the former group. While the age cut-off values for defining young cohorts vary across studies, all investigations have consistently demonstrated that younger patients tend to present with more aggressive clinicopathological features [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e, \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e, \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. The increased proportion of mucinous adenocarcinoma and signet-ring cell carcinoma in patients with young-onset CRC currently lacks a definitive pathological explanation, necessitating future investigations using multi-omics approaches (including genomic, transcriptomic, and gut microbiome profiling) to elucidate the underlying mechanisms. In China, current guidelines recommend initiating CRC screening at the age of 50 years for asymptomatic average-risk individuals. Younger patients with CRC frequently present with advanced-stage disease at diagnosis, potentially due to inadequate screening participation and/or nonspecific clinical manifestations.\u003c/p\u003e \u003cp\u003eSimilar to the findings of prior studies [\u003cspan additionalcitationids=\"CR17\" citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e] the MSI-H/dMMR rate was elevated in the younger cohort (28.65% vs. 12.81%), with MSS/pMMR accounting for most cases (71.35%). Subsequently, we sought to explore potential differences in the gene expression profiles between the two MSS/pMMR patient groups. Consistent with previous findings, \u003cem\u003eTP53\u003c/em\u003e, \u003cem\u003eAPC\u003c/em\u003e, and \u003cem\u003eKRAS\u003c/em\u003e remained the most frequently mutated oncogenic drivers in both young and older CRC cohorts [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. Following MSI, \u003cem\u003eKRAS\u003c/em\u003e is the second most clinically significant molecular biomarker in CRC, with a mutation prevalence of 40\u0026ndash;50%. Notably, patients with CRC carrying \u003cem\u003eKRAS\u003c/em\u003e mutations in exons 2\u0026ndash;4 demonstrate complete resistance to anti-epidermal growth factor receptor therapies. In line with observations in younger patients (\u0026le;\u0026thinsp;40 years) [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e], this study confirms that colorectal cancer patients aged\u0026thinsp;\u0026le;\u0026thinsp;30 years with MSS status also exhibit a lower frequency of \u003cem\u003eKRAS\u003c/em\u003e mutations.\u003c/p\u003e \u003cp\u003eCurrently, the fundamental mechanism underlying the more aggressive biological behavior of colorectal cancer in younger patients remains undetermined. Therefore, this study investigates the differences in gene expression profiles between the two age groups from a genetic perspective, aiming to identify potential molecular associations. Our extensive screening of 1021 genes demonstrated that, beyond \u003cem\u003eKRAS\u003c/em\u003e, there were no other significant differences in the alternation frequencies between the younger and older MSS patient groups. This highlights that within a rigorously defined MSS population, the mutational landscape can appear remarkably stable. The research by Richarda et al. on MSS CRC demonstrated that adolescent patients (\u0026le;\u0026thinsp;25 years) in their cohort exhibited significantly higher \u003cem\u003eTP53\u003c/em\u003e mutation rates yet lower \u003cem\u003eAPC\u003c/em\u003e mutation frequencies than did older adult patients (\u0026gt;\u0026thinsp;60 years) from The Cancer Genome Atlas database [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. Furthermore, Lieu et al. recently reported a higher \u003cem\u003eTP53\u003c/em\u003e mutation rates and lower \u003cem\u003eAPC\u003c/em\u003e mutation frequency in MSS CRCs diagnosed before the age of 40 years than they did in those diagnosed over the age of 50 years [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]. Conversely, Salem et al. found a higher \u003cem\u003eAPC\u003c/em\u003e mutation frequency in a similar young-onset patient cohort [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]. Nonetheless, both the current study and another Asian report found no significant differences in \u003cem\u003eTP53\u003c/em\u003e mutation rates between the two patient groups [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]. These inconsistencies are likely attributable to considerable heterogeneity in study cohorts, including differences in age cut-offs, geographical and ethnic backgrounds, sample sizes, and the potential inclusion of undiagnosed hereditary syndromes.\u003c/p\u003e \u003cp\u003ePrevious research has reported conflicting outcomes between younger and older patients with CRC. If patients with CRC are younger than 40 or 50 [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e, \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e] years of age, their prognosis improves when compared to that of older patients. This may be mainly due to their healthier baseline status and comorbidity absence. However, other studies have demonstrated that young-onset patients with CRC tend to present with more advanced disease at diagnosis, leading to worse outcomes and survival rates than those of older patients [\u003cspan additionalcitationids=\"CR27\" citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]. Owing to a general lack of awareness of CRC among younger individuals, early symptoms are often mistaken for poor diet or gastrointestinal disorders, delaying the optimal window for diagnosis and treatment. This delay may cause tumour progression to more severe conditions with deeper infiltration or metastasis, thereby increasing treatment difficulty and worsening the prognosis [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. The present study revealed no significant prognosis difference between the two age groups. Previous research indicated that younger patients could undergo more aggressive surgical and perioperative treatments, potentially explaining the similar outcomes between age groups [\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e, \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e].\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eIn conclusion, our study delineates a distinct profile for young MSS colorectal cancer patients, characterized by aggressive clinicopathological features and a uniquely lower KRAS mutation frequency. The key finding\u0026mdash;the absence of other significant genomic differences across a 1021-gene panel\u0026mdash;strongly suggests that the aggressive phenotype in these young patients is not driven by a higher burden of somatic mutations in common cancer genes. Instead, their aggressive clinical behaviour may involve alternative mechanisms. The primary limitation of this work is its limited cohort size, necessitating validation in larger, multi-centre studies. Future research should prioritize integrated multi-omics approaches to unravel the drivers of this clinically challenging entity.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cp\u003e\u003cstrong\u003eCRC\u003c/strong\u003e Colorectal Cancer\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMMR\u003c/strong\u003e Mismatch Repair\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003epMMR\u003c/strong\u003e Proficient Mismatch Repair\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003edMMR\u003c/strong\u003e Deficient Mismatch Repair\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMSI\u003c/strong\u003e Microsatellite Instability\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMSI-H\u003c/strong\u003e Microsatellite Instability-High\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMSI-L\u003c/strong\u003e Microsatellite Instability-Low\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMSS\u003c/strong\u003e Microsatellite Stable\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTNM\u003c/strong\u003e\u0026nbsp; Tumour\u0026ndash;Node\u0026ndash;Metastasis\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003ePFS\u003c/strong\u003e Progression-Free Survival\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003ePCR\u003c/strong\u003e Polymerase Chain Reaction\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eNGS\u003c/strong\u003e Next-Generation Sequencing\u0026nbsp;\u003c/p\u003e"},{"header":"Declarations","content":" \u003cp\u003e \u003cstrong\u003eEthics approval and consent to participate\u003c/strong\u003e \u003cp\u003e This retrospective cohort study was reviewed and approved by the Institutional Ethics Committee of the Affiliated Cancer Hospital of Zhengzhou University (No.2022-318-001). The requirement for written informed consent was waived by the aforementioned ethics committee due to the retrospective nature of the study, which involved the analysis of anonymized existing data. All procedures performed in studies involving human participants were in accordance with the ethical standards of institutional and/or national research committees, as well as with the 1964 Helsinki declaration and its later amendments.\u003c/p\u003e \u003c/p\u003e \u003cp\u003e \u003cstrong\u003eConsent for publication\u003c/strong\u003e \u003cp\u003eThis study contains no personally identifiable data. Approval for publication was obtained from all authors.\u003c/p\u003e \u003c/p\u003e\u003cp\u003e \u003ch2\u003eCompeting interests\u003c/h2\u003e \u003cp\u003eWe declare no competing interests.\u003c/p\u003e \u003c/p\u003e\u003ch2\u003eFunding\u003c/h2\u003e \u003cp\u003eThis study was supported by the Henan Province Medical Science and Technology Research Program [Grant No.: LHGJ20250196].\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eQ.X. conceived and designed the study. B.Z., C.Z., Y.W. and Y.Z. collected the clinical data and conducted telephone follow-ups. Y.J. performed the statistical analysis. Y.W. (Yuanyuan Wang) wrote the main manuscript text. Y.Y. prepared the figures. All authors reviewed the manuscript.\u003c/p\u003e\u003ch2\u003eAcknowledgements\u003c/h2\u003e \u003cp\u003eNone.\u003c/p\u003e\u003ch2\u003eData Availability\u003c/h2\u003e\u003cp\u003eThe datasets generated and analysed during this study are available from the corresponding author upon reasonable request.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eSung H, Ferlay J, Siegel RL, Laversanne M, Soerjomataram I, Jemal A, et al. Global Cancer Statistics 2020: GLOBOCAN Estimates of Incidence and Mortality Worldwide for 36 Cancers in 185 Countries. CA Cancer J Clin. 2021;71(3):209\u0026ndash;49.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBrenner DR, Ruan Y, Shaw E, De P, Heitman SJ, Hilsden RJ. Increasing colorectal cancer incidence trends among younger adults in Canada. Prev Med. 2017;105:345\u0026ndash;9.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAraghi M, Soerjomataram I, Bardot A, Ferlay J, Cabasag CJ, Morrison DS, et al. Changes in colorectal cancer incidence in seven high-income countries: a population-based study. Lancet Gastroenterol Hepatol. 2019;4(7):511\u0026ndash;8.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eTanaka LF, Figueroa SH, Popova V, Klug SJ, Buttmann-Schweiger N. The Rising Incidence of Early-Onset Colorectal Cancer. Dtsch Arztebl Int. 2023;120(Forthcoming):59\u0026ndash;64.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAndr\u0026eacute; T, Shiu KK, Kim TW, Jensen BV, Jensen LH, Punt C, et al. Pembrolizumab in Microsatellite-Instability-High Advanced Colorectal Cancer. N Engl J Med. 2020;383(23):2207\u0026ndash;18.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZhang C, Ding H, Sun S, Luan Z, Liu G, Li Z. 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J Gastrointest Surg. 2020;24(10):2416\u0026ndash;22.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePatel SG, Murphy CC, Lieu CH, Hampel H. Early age onset colorectal cancer. Adv Cancer Res. 2021;151:1\u0026ndash;37.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLui RN, Tsoi KKF, Ho JMW, Lo CM, Chan FCH, Kyaw MH, et al. Global Increasing Incidence of Young-Onset Colorectal Cancer Across 5 Continents: A Joinpoint Regression Analysis of 1,922,167 Cases. Cancer Epidemiol Biomarkers Prev. 2019;28(8):1275\u0026ndash;82.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eUeno A, Yokota M, Ueno M, Kawamoto K. Colorectal cancer in adolescent and young adults: epidemiology in Japan and narrative review. J Gastrointest Oncol. 2023;14(4):1856\u0026ndash;68.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eFranklyn J, Lomax J, Labib PLZ, Baker A, Balasubramanya S, Natale J, et al. 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Transl Gastroenterol Hepatol. 2025;10:30.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWang W, Wang R, Han X, Zhang W, Zhu L, Gu Y. Epidemiological and clinicopathological features of KRAS, NRAS, BRAF mutations and MSI in Chinese patients with stage I-III colorectal cancer. Med (Baltim). 2024;103(14):e37693.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZhang J, Li S, Ma P, Zhang J, Cao Y, Liu C, et al. Clinicopathological features and prognoses in younger and older patients with mismatch repair defects colorectal cancer: a retrospective comparative cohort study. J Gastrointest Oncol. 2024;15(1):260\u0026ndash;70.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLi J, Pan Y, Guo F, Wang C, Liang L, Li P, et al. Patterns in genomic mutations among patients with early-onset colorectal cancer: an international, multicohort, observational study. 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Oncologist. 2020;25(5):404\u0026ndash;13.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePonvilawan B, Sakornsakolpat P, Pongpaibul A, Roothumnong E, Akewanlop C, Pithukpakorn M, et al. Comprehensive genomic analysis in sporadic early-onset colorectal adenocarcinoma patients. BMC Cancer. 2025;25(1):349.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAbdollahi M, Kasiri N, Pourhoseingholi MA, Baghestani AR, Esmaily H. Determination of Cut Point in the Age of Colorectal Cancer Diagnosis Using a Survival Cure Model. Asian Pac J Cancer Prev. 2019;20(9):2819\u0026ndash;23.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eChen F, Chen J, Luo D, Zhang R, Yang Y, Li Q, et al. Prognosis and clinicopathological features of patients with early-onset and late-onset colorectal cancer with second primary malignancies. J Gastroenterol Hepatol. 2025;40(1):133\u0026ndash;41.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAkoury ER, Smolenschi C, Masri N, Hollebecque A, Boige V, El Rawadi EJ, et al. 75P Clinical and molecular characteristics of young onset colorectal cancers. Ann Oncol. 2025;36:S40.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eFu JF, Huang YQ, Yang J, Yi CH, Chen HL, Zheng S. Clinical characteristics and prognosis of young patients with colorectal cancer in Eastern China. World J Gastroenterol. 2013;19(44):8078\u0026ndash;84.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLewis SL, Stewart KE, Garwe T, Sarwar Z, Morris KT. Association of Age and Overall Survival in Surgically Resected Colorectal Cancer Patients. J Surg Res. 2023;281:321\u0026ndash;7.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eUgai T, Haruki K, Harrison TA, Cao Y, Qu C, Chan AT, et al. Molecular Characteristics of Early-Onset Colorectal Cancer According to Detailed Anatomical Locations: Comparison With Later-Onset Cases. Am J Gastroenterol. 2023;118(4):712\u0026ndash;26.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBurnett-Hartman AN, Powers JD, Chubak J, Corley DA, Ghai NR, McMullen CK, et al. Treatment patterns and survival differ between early-onset and late-onset colorectal cancer patients: the patient outcomes to advance learning network. Cancer Causes Control. 2019;30(7):747\u0026ndash;55.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"bmc-cancer","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"bcan","sideBox":"Learn more about [BMC Cancer](http://bmccancer.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/bcan/default.aspx","title":"BMC Cancer","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"colorectal cancer, ≤30 years, microsatellite instability, MSS","lastPublishedDoi":"10.21203/rs.3.rs-8390621/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8390621/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eBackground\u003c/h2\u003e \u003cp\u003eThe biological and clinical heterogeneity of younger patients with microsatellite stable (MSS)/proficient mismatch repair (pMMR) colorectal cancer (CRC) is largely unexplored. This retrospective study compared the clinicopathological factors, prognosis, and molecular characteristics of MSS/pMMR CRC in patients younger and older than 30 years.\u003c/p\u003e\u003ch2\u003eMethods\u003c/h2\u003e \u003cp\u003eOverall, 191 and 573 younger (\u0026le;\u0026thinsp;30 years old) and older (\u0026gt;\u0026thinsp;30 years old) CRC patients, respectively, were enrolled. Statistically significant differences between the groups were determined using the \u003cem\u003eχ\u003c/em\u003e\u003csup\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sup\u003e or Fisher's exact test. Progression-free survival (PFS) was assessed by Kaplan-Meier analysis and compared using log-rank test.\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e \u003cp\u003eYounger patients with MSS/pMMR CRC exhibited significantly more aggressive features, including higher rates of mucinous adenocarcinoma, poor differentiation, deeper tumour invasion and advanced tumour\u0026ndash;node\u0026ndash;metastasis (TNM) stage than older patients. Molecular analysis revealed a higher microsatellite instability-high (MSI-H) incidence but lower \u003cem\u003eKRAS\u003c/em\u003e mutation frequency in younger patients compared to older individuals. Furthermore, comprehensive genetic profiling of 1021 genes revealed no additional significant variations and no significant differences in PFS between the two MSS/pMMR CRC groups.\u003c/p\u003e\u003ch2\u003eConclusion\u003c/h2\u003e \u003cp\u003eYounger patients with CRC exhibit unique biological behaviour. Therefore, unravelling the mechanisms of its aggressiveness through integrated multi-omics technologies should be a key focus in future research.\u003c/p\u003e","manuscriptTitle":"Clinicopathological, Prognostic, and Molecular Differences Between Microsatellite-Stable Colorectal Cancer Patients Aged ≤ 30 Years and \u0026gt;30 Years","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-01-29 00:49:53","doi":"10.21203/rs.3.rs-8390621/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2026-03-09T18:45:37+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-03-09T18:30:00+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-03-01T12:22:31+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"282766683403235921088147294742536721183","date":"2026-02-12T08:49:41+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"115266176757754798070792509565360021418","date":"2026-02-10T13:53:05+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"38891270501009225231763635099736519229","date":"2026-02-05T07:54:06+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2026-01-23T16:06:10+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2026-01-13T18:10:15+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2026-01-02T14:59:05+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-12-30T11:23:17+00:00","index":"","fulltext":""},{"type":"submitted","content":"BMC Cancer","date":"2025-12-30T11:13:35+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"bmc-cancer","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"bcan","sideBox":"Learn more about [BMC Cancer](http://bmccancer.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/bcan/default.aspx","title":"BMC Cancer","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"236e055b-e766-444c-a04a-c5187feff74d","owner":[],"postedDate":"January 29th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"in-revision","subjectAreas":[],"tags":[],"updatedAt":"2026-05-18T08:24:22+00:00","versionOfRecord":[],"versionCreatedAt":"2026-01-29 00:49:53","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8390621","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8390621","identity":"rs-8390621","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}