Detection of an Isolated Solitary Brain Metastasis from Colon Adenocarcinoma via 18F-FDG PET/CT: A Rare Case and Its Multimodal Management

Detection of an Isolated Solitary Brain Metastasis from Colon Adenocarcinoma via 18F-FDG PET/CT: A Rare Case and Its Multimodal Management | 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 Case Report Detection of an Isolated Solitary Brain Metastasis from Colon Adenocarcinoma via 18F-FDG PET/CT: A Rare Case and Its Multimodal Management Nilüfer BIÇAKCI, Fatih BATI This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6812456/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 26 Jun, 2025 Read the published version in The Journal of Diagnostic and Theranostic Imaging → Version 1 posted You are reading this latest preprint version Abstract Background: Brain metastasis (BM) is observed in approximately 1–4% of cases involving metastatic colon cancer and is almost invariably associated with extracranial dissemination. The occurrence of isolated intracranial disease in the absence of systemic metastases is, therefore, exceedingly rare. Case presentation: We report a 74 year-old female who presented with new-onset focal seizures 18 months after curative surgery for stage IIIC sigmoid adenocarcinoma. The F18 FDG PET/CT scan revealed increased F18 FDG uptake in an 18x19 mm hyperdense lesion located in the right temporal lobe, accompanied by a substantial edematous region in the surrounding area (SUV max:8.0) but no abnormal F18 FDG accumulation elsewhere, confirming isolated BM. Brain MRI revealed a 28x30 mm contrast-enhancing lesion in the right temporal lobe with vasogenic edema. The patient underwent gross-total resection followed by adjuvant stereotactic radiosurgery (SRS, 18 Gy single fraction). Histopathology showed metastatic moderately-differentiated colon adenocarcinoma (CK20+, CDX-2+, CK7+, P53+). Post-operative capecitabine plus bevacizumab was given for six cycles. At 12-month follow-up the patient remains disease-free on surveillance MRI and F18 PET/CT. Conclusion: This case illustrates the diagnostic value of F18 FDG PET/CT in excluding extracranial disease and supports an aggressive local-therapy strategy (surgery ± SRS) for solitary kolon adenocarsinoma BM, which may confer prolonged survival. Nuclear Medicine & Medical Imaging colon cancer solitary brain metastasis F18 FDG PET/CT Figures Figure 1 Figure 2 Introduction Brain metastases occur in only 0.3–3.2% of patients with colorectal cancer (CRC) and in approximately 1% of those presenting with metastatic disease ( 1 , 2 ). When present, these metastases are almost invariably associated with liver and/or lung metastases; genuinely solitary intracranial disease accounts for less than 2% of cases ( 2 ). In carefully selected patients, aggressive local therapy, such as surgery with or without stereotactic radiosurgery (SRS), can extend median overall survival (OS) from 4–8 months to 12–24 months ( 3 ). We describe an exceptional case of isolated brain metastasis from previously resected CRC detected via PET/CT and discuss diagnostic and therapeutic considerations in light of contemporary evidence. Case Presentation A 74-year-old female was disease-free after laparoscopic anterior resection for pT4a pN2b M0 (stage IIIC) sigmoid adenocarcinoma and adjuvant FOLFOX. Two years later the patient developed focal motor seizures of the left upper limb. There was no headache, visual disturbance, or systemic symptom. Neurological exam showed subtle left pronator drift; Karnofsky Performance Status was 90. No stigmata of extracranial recurrence were present. Modality Findings Interpretation The F18 FDG PET/CT scan revealed increased F18 FDG uptake in an 18x19 mm hyperdense lesion located in the right temporal lobe, accompanied by a substantial edematous region in the surrounding area (SUV max:8.0) but no abnormal F18 FDG accumulation elsewhere, confirming isolated BM. Brain MRI revealed a 28x30 mm contrast-enhancing lesion in the right temporal lobe with vasogenic edema ( Figure 1 ). Therapeutic intervention Neuronavigation-guided craniotomy achieved gross-total resection. Pathology: metastatic moderately-differentiated adenocarcinoma, CK20+, CDX-2+, CK7-, P53+ identical KRAS exon 2 mutation as primary. Post-operative SRS (18 Gy single fraction) was delivered to the resection cavity. Six cycles of capecitabine + bevacizumab were administered. Follow-up and outcomes MRI at 3, 6, and 12 months showed no recurrence; FDG PET/CT at 12 months remained negative for systemic disease ( Figure 2 ). The patient is seizure-free, on levetiracetam, with KPS 100. Discussion Epidemiology and routes of spread Extensive population-based datasets indicate that brain metastases (BM) occur in ≤3% of colorectal cancer (CRC) patients, typically manifesting at a later stage (1). Systematic reviews reveal that less than 2% of these patients present with truly isolated intracranial disease (2). Identified risk factors include younger age, right-sided primary tumors, KRAS or HER2 alterations, and, most significantly, concurrent pulmonary metastases (4). While hematogenous dissemination via the pulmonary arterial "filter-and-seed" mechanism is prevalent, venous reflux through Batson’s valveless vertebral plexus can bypass the lungs, accounting for rare solitary BM cases, as observed in our patient (5). Early isolated presentations have also been documented in single-institution case reports, highlighting the necessity for neurological vigilance even when systemic imaging results are negative (15). Imaging considerations Contrast-enhanced MRI continues to be the gold standard for intracranial staging. Whole-body 18F-FDG PET/CT, despite its high physiological cortical uptake, is crucial for the exclusion of occult extracranial disease, thereby supporting the justification for curative-intent local therapy (6). Emerging tracers such as 18F-FET and 68Ga-PSMA, along with hybrid PET/MRI, have the potential to enhance lesion detection and improve the differentiation between radiation necrosis and recurrence (6). Management strategies Given the relative radio- and chemo-resistance of colorectal cancer brain metastases (CRC BM), the recommended approach for solitary lesions in patients with adequate fitness is maximal safe resection followed by focal radiotherapy. A meta-analysis conducted in 2022, encompassing 1,438 patients, demonstrated superior overall survival (OS) for metastasectomy compared to radiotherapy alone, with a hazard ratio of 0.53 (7). Multicenter series on stereotactic radiosurgery (SRS) report 12-month local control rates approaching 80% when marginal doses of ≥25 Gy are administered (8,9). Retrospective data comparing single-fraction SRS (median 20 Gy) with multi-fraction SRS indicate comparable local control and toxicity, thereby offering flexibility in dose-fractionation for radio-resistant colorectal histology (17). Post-operative whole-brain radiotherapy (WBRT) is currently designated for cases involving multiple lesions or leptomeningeal disease. Randomized trials have demonstrated that WBRT offers equivalent survival outcomes but results in greater neuro-cognitive toxicity compared to postoperative stereotactic radiosurgery (SRS) (10). The current EANO–ESMO guidelines similarly advocate for postoperative cavity SRS or hypofractionated stereotactic radiotherapy over routine WBRT to preserve neuro-cognitive function in patients with resected solitary metastases (16). Systemic therapy generally aligns with standard metastatic colorectal cancer (mCRC) regimens. Retrospective studies suggest that capecitabine, oxaliplatin, and bevacizumab exhibit some activity within the central nervous system, with bevacizumab providing a modest overall survival benefit (11–13). Additionally, HER2-amplified colorectal cancer may respond to tucatinib-based combinations, and immune-checkpoint inhibition is under investigation for tumors deficient in mismatch repair (14). Prognosis Independent predictors of extended survival include the presence of a single brain metastasis (BM), a Karnofsky Performance Status (KPS) greater than 70, a controlled primary tumor and extracranial disease, and an interval exceeding 12 months from the initial colorectal cancer (CRC) diagnosis (2,4,12). Our patient met all these favorable criteria and remains disease-free 12 months following multimodal therapy. Future directions Prospective trials are needed to define optimal systemic partners for local therapy and to refine SRS dose-fractionation schemes for radio-resistant colorectal histology. Molecular PET tracers hold promise for earlier detection and response assessment. Declarations The authors confirm that the patient described in their case report provided written informed consent to participate in the study and to have the case details and images published. Conflict of interest: None declared. Funding: No external funding. References Cagney DN, Martin AM, Catalano PJ, Lin NU, Lee EQ. Incidence and prognosis of patients with brain metastases at diagnosis of systemic malignancy: a population-based study. Neuro Oncol . 2017;19(11):1511-21. Müller S, Köhler F, Hendricks A, Maihöfer C, Makowiec F. Brain metastases from colorectal cancer: a systematic review and meta-analysis to establish a guideline for daily treatment. Cancers (Basel) . 2021;13(4):900. Mjahed RB, Astaras C, Roth A, Koessler T. Where are we now and where might we be headed in understanding and managing brain metastases in colorectal cancer patients? Curr Treat Options Oncol . 2022;23(7):980-1000. doi:10.1007/s11864-022-00982-0. Chen Q, He L, Li Y, Zuo C, Li M, Wu X, et al. Risk factors on the incidence and prognostic effects of colorectal cancer with brain metastasis: a SEER-based study. Front Oncol . 2022;12:758681. doi:10.3389/fonc.2022.758681. Batson OV. The function of the vertebral veins and their role in the spread of metastases. Ann Surg . 1940;112(1):138-49. Schroeder HW, Hall LT. Molecular imaging of brain metastases with positron emission tomography. In: Metastasis: Clinical and Biological Perspectives . Exon Publishing; 2022. p. 233-49. Chang Y, Wong CE, Lee PH, Ng DC, Cheung SH. Survival outcome of surgical resection versus radiotherapy in brain metastasis from colorectal cancer: a meta-analysis. Front Med (Lausanne) . 2022;9:768896. Navarria P, Mazzarella A, Clerici E, Ascolese AM, Franzese C, Tomatis S, et al. Stereotactic radiosurgery for brain metastases from colorectal cancer: a multicentre study. Acta Oncol . 2020;59(9):1118-26. Chernov M, Hayashi M. Radiosurgery for brain metastases of colorectal cancer. Br J Radiol . 2022;95(1136):20210179. doi:10.1259/bjr.20210179. Brown PD, Ballman KV, Cerhan JH, Anderson SK, Carrero XW, Whitton AC, et al. Postoperative stereotactic radiosurgery compared with whole-brain radiotherapy for resected metastatic brain disease: a randomized controlled trial. Lancet Oncol . 2017;18(8):1049-60. Kim DY, Ryu CG, Jung EJ, Paik JH, Hwang DY. Brain metastasis from colorectal cancer: a single center experience. Ann Surg Treat Res . 2018;94(1):13-8. doi:10.4174/astr.2018.94.1.13. Wang D, Chen C, Ge X, Yang Q, Huang Y, Ling T, et al. Factors prognostic for brain metastases from colorectal cancer: a single-center experience in China. Cancer Manag Res . 2021;13:6767-74. doi:10.2147/CMAR.S320179. Li W, Wang T, Zhu Y, Liu H, Xu J. Brain metastasis from colorectal cancer: treatment, survival, and prognosis. Medicine (Baltimore) . 2022;101(40):e30273. Hewish M, Lord CJ, Martin SA, Cunningham D, Ashworth A. Mismatch repair deficient colorectal cancer in the era of personalized treatment. Nat Rev Clin Oncol . 2010;7(4):197-208. doi:10.1038/nrclinonc.2010.18. Piljic H, Demir U, Ozcan M, Ozturk E. Precocious brain metastasis of colorectal carcinoma—report of two cases. Turk J Colorectal Dis . 2017;27(1):34-7. Le Rhun E, Guckenberger M, Smits M, Dummer R, Bachelot T, Sahm F, et al. EANO-ESMO Clinical Practice Guidelines for diagnosis, treatment and follow-up of patients with brain metastasis from solid tumours. Ann Oncol . 2021;32(11):1332-47. doi:10.1016/j.annonc.2021.07.016. Li Y, Wu J, Liu F, Shao X, Liang X, Zhang F, et al. Single-fraction SRS and multiple-fraction SRT for brain metastases from colorectal cancer. Front Oncol . 2022;12:1060570. doi:10.3389/fonc.2022.1060570. Additional Declarations The authors declare no competing interests. Cite Share Download PDF Status: Published Journal Publication published 26 Jun, 2025 Read the published version in The Journal of Diagnostic and Theranostic Imaging → Version 1 posted 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. 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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-6812456","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Case Report","associatedPublications":[],"authors":[{"id":466425657,"identity":"b3c2d0e8-5586-48bf-8960-d1e64936ce11","order_by":0,"name":"Nilüfer BIÇAKCI","email":"","orcid":"https://orcid.org/0000-0003-4124-1225","institution":"Nuclear Medicine Clinic, Samsun Education and Research Hospital, Samsun, Türkiye","correspondingAuthor":false,"prefix":"","firstName":"Nilüfer","middleName":"","lastName":"BIÇAKCI","suffix":""},{"id":466426489,"identity":"2952a255-13ea-42bf-836e-700321d241c3","order_by":1,"name":"Fatih BATI","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA+UlEQVRIie3QsUvDQBTH8Z88uCwvdK2E6r9wEigUkfwrHlkFHTuFgINLSlcH/4hMJ25X3uDoKthFAp0ULAVBUDBNQRRJ1M3hvuM7PrzHAT7fPyzIAQEcQOQ+pv0uwo42hEkdfia6k1BDwPqXJLiZyQnmu0nAq6eXo8xcgmZ3jNfjVsIp5ByLvYJCuz2xYq5yle4z9ChvIQlqwpCtNUFonSkdD6OatF7GvaohSUFcLd9sVpPeczfpb7aYmiAKLa23qB9IpYX1Ii1EDaOBlbgUFY8udNxxmKlWPJ4fnE2lWj7abFBen97fPox32n+56cszfZv4fD6f76+9Aww3UDYlZnSoAAAAAElFTkSuQmCC","orcid":"https://orcid.org/0000-0003-3241-6417","institution":"Department of Nuclear Medicine, Faculty of Medicine, Samsun University, Samsun, Türkiye","correspondingAuthor":true,"prefix":"","firstName":"Fatih","middleName":"","lastName":"BATI","suffix":""}],"badges":[],"createdAt":"2025-06-03 14:38:30","currentVersionCode":1,"declarations":{"humanSubjects":true,"vertebrateSubjects":false,"conflictsOfInterestStatement":false,"humanSubjectEthicalGuidelines":true,"humanSubjectConsent":true,"humanSubjectClinicalTrial":true,"humanSubjectCaseReport":true,"vertebrateSubjectEthicalGuidelines":false},"doi":"10.21203/rs.3.rs-6812456/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6812456/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.5455/TheJODTi.1606.2404","type":"published","date":"2025-06-27T00:00:00+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":84205315,"identity":"0e05d685-7559-4610-a026-456d46f91e71","added_by":"auto","created_at":"2025-06-09 09:03:36","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":345498,"visible":true,"origin":"","legend":"\u003cp\u003eThe axial CT (right), fused (middle), and PET (left) brain images of brain-included whole-body FDG PET/CT showing right temporal lesion (black arrow) that appears as a subtle hypodense area in CT with max SUV 8.0. The primary tumor turned out to be colon adenocarcinoma.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-6812456/v1/d6c44430ba9a98594059a876.png"},{"id":84203882,"identity":"1336e721-1db9-49fb-9737-0cac24273870","added_by":"auto","created_at":"2025-06-09 08:47:37","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":175997,"visible":true,"origin":"","legend":"\u003cp\u003eThe axial CT (right), fused (middle), and PET (left) brain images obtained from a whole-body FDG PET/CT scan, which included the brain, indicate that the patient underwent a gross-total resection followed by adjuvant stereotactic radiosurgery (SRS, 18 Gy single fraction).\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-6812456/v1/e5ffc0277c0220ed7fa5ad1e.png"},{"id":86977605,"identity":"18c13ade-728c-4f4e-9e75-6a714774a9ad","added_by":"auto","created_at":"2025-07-17 22:47:43","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1158309,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6812456/v1/ac0fb4b5-0bf6-4ce2-9d48-fa230af8a7b9.pdf"}],"financialInterests":"The authors declare no competing interests.","formattedTitle":"\u003cp\u003eDetection of an Isolated Solitary Brain Metastasis from Colon Adenocarcinoma via 18F-FDG PET/CT: A Rare Case and Its Multimodal Management\u003c/p\u003e","fulltext":[{"header":"Introduction","content":"\u003cp\u003eBrain metastases occur in only 0.3\u0026ndash;3.2% of patients with colorectal cancer (CRC) and in approximately 1% of those presenting with metastatic disease (\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e). When present, these metastases are almost invariably associated with liver and/or lung metastases; genuinely solitary intracranial disease accounts for less than 2% of cases (\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e). In carefully selected patients, aggressive local therapy, such as surgery with or without stereotactic radiosurgery (SRS), can extend median overall survival (OS) from 4\u0026ndash;8 months to 12\u0026ndash;24 months (\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e). We describe an exceptional case of isolated brain metastasis from previously resected CRC detected via PET/CT and discuss diagnostic and therapeutic considerations in light of contemporary evidence.\u003c/p\u003e"},{"header":"Case Presentation","content":"\u003cp\u003eA 74-year-old female was disease-free after laparoscopic anterior resection for pT4a pN2b M0 (stage IIIC) sigmoid adenocarcinoma and adjuvant FOLFOX. Two years later the patient developed focal motor seizures of the left upper limb. There was no headache, visual disturbance, or systemic symptom.\u003c/p\u003e\n\u003cp\u003eNeurological exam showed subtle left pronator drift; Karnofsky Performance Status was 90. No stigmata of extracranial recurrence were present.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eModality Findings Interpretation\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe F18 FDG PET/CT scan revealed increased F18 FDG uptake in an 18x19 mm hyperdense lesion located in the right temporal lobe, accompanied by a substantial edematous region in the surrounding area (SUV max:8.0) but no abnormal F18 FDG accumulation elsewhere, confirming isolated BM. Brain MRI revealed a 28x30 mm contrast-enhancing lesion in the right temporal lobe with vasogenic edema (\u003cstrong\u003eFigure 1\u003c/strong\u003e).\u003c/p\u003e\n\u003cp\u003eTherapeutic intervention\u0026emsp;Neuronavigation-guided craniotomy achieved gross-total resection. Pathology: metastatic moderately-differentiated adenocarcinoma, CK20+, CDX-2+, CK7-, P53+ identical KRAS exon 2 mutation as primary. Post-operative SRS (18 Gy single fraction) was delivered to the resection cavity. Six cycles of capecitabine + bevacizumab were administered. Follow-up and outcomes MRI at 3, 6, and 12 months showed no recurrence; FDG PET/CT at 12 months remained negative for systemic disease (\u003cstrong\u003eFigure 2\u003c/strong\u003e). The patient is seizure-free, on levetiracetam, with KPS 100.\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003e\u003cstrong\u003eEpidemiology and routes of spread\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eExtensive population-based datasets indicate that brain metastases (BM) occur in \u0026le;3% of colorectal cancer (CRC) patients, typically manifesting at a later stage (1). Systematic reviews reveal that less than 2% of these patients present with truly isolated intracranial disease (2). Identified risk factors include younger age, right-sided primary tumors, KRAS or HER2 alterations, and, most significantly, concurrent pulmonary metastases (4). While hematogenous dissemination via the pulmonary arterial \u0026quot;filter-and-seed\u0026quot; mechanism is prevalent, venous reflux through Batson\u0026rsquo;s valveless vertebral plexus can bypass the lungs, accounting for rare solitary BM cases, as observed in our patient (5). Early isolated presentations have also been documented in single-institution case reports, highlighting the necessity for neurological vigilance even when systemic imaging results are negative (15).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eImaging considerations\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eContrast-enhanced MRI continues to be the gold standard for intracranial staging. Whole-body 18F-FDG PET/CT, despite its high physiological cortical uptake, is crucial for the exclusion of occult extracranial disease, thereby supporting the justification for curative-intent local therapy (6). Emerging tracers such as 18F-FET and 68Ga-PSMA, along with hybrid PET/MRI, have the potential to enhance lesion detection and improve the differentiation between radiation necrosis and recurrence (6).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eManagement strategies\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eGiven the relative radio- and chemo-resistance of colorectal cancer brain metastases (CRC BM), the recommended approach for solitary lesions in patients with adequate fitness is maximal safe resection followed by focal radiotherapy. A meta-analysis conducted in 2022, encompassing 1,438 patients, demonstrated superior overall survival (OS) for metastasectomy compared to radiotherapy alone, with a hazard ratio of 0.53 (7). Multicenter series on stereotactic radiosurgery (SRS) report 12-month local control rates approaching 80% when marginal doses of \u0026ge;25 Gy are administered (8,9). Retrospective data comparing single-fraction SRS (median 20 Gy) with multi-fraction SRS indicate comparable local control and toxicity, thereby offering flexibility in dose-fractionation for radio-resistant colorectal histology (17).\u003c/p\u003e\n\u003cp\u003ePost-operative whole-brain radiotherapy (WBRT) is currently designated for cases involving multiple lesions or leptomeningeal disease. Randomized trials have demonstrated that WBRT offers equivalent survival outcomes but results in greater neuro-cognitive toxicity compared to postoperative stereotactic radiosurgery (SRS) (10). The current EANO\u0026ndash;ESMO guidelines similarly advocate for postoperative cavity SRS or hypofractionated stereotactic radiotherapy over routine WBRT to preserve neuro-cognitive function in patients with resected solitary metastases (16). Systemic therapy generally aligns with standard metastatic colorectal cancer (mCRC) regimens. Retrospective studies suggest that capecitabine, oxaliplatin, and bevacizumab exhibit some activity within the central nervous system, with bevacizumab providing a modest overall survival benefit (11\u0026ndash;13). Additionally, HER2-amplified colorectal cancer may respond to tucatinib-based combinations, and immune-checkpoint inhibition is under investigation for tumors deficient in mismatch repair (14).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003ePrognosis\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eIndependent predictors of extended survival include the presence of a single brain metastasis (BM), a Karnofsky Performance Status (KPS) greater than 70, a controlled primary tumor and extracranial disease, and an interval exceeding 12 months from the initial colorectal cancer (CRC) diagnosis (2,4,12). Our patient met all these favorable criteria and remains disease-free 12 months following multimodal therapy.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFuture directions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eProspective trials are needed to define optimal systemic partners for local therapy and to refine SRS dose-fractionation schemes for radio-resistant colorectal histology. Molecular PET tracers hold promise for earlier detection and response assessment.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cspan\u003eThe authors confirm that the patient described in their case report provided written informed consent to participate in the study and to have the case details and images published.\u003c/span\u003e\u003c/p\u003e\u003cp\u003e\u003cstrong\u003eConflict of interest:\u003c/strong\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eNone declared.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding:\u003c/strong\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eNo external funding.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n \u003cli\u003eCagney DN, Martin AM, Catalano PJ, Lin NU, Lee EQ. Incidence and prognosis of patients with brain metastases at diagnosis of systemic malignancy: a population-based study. \u003cem\u003eNeuro Oncol\u003c/em\u003e. 2017;19(11):1511-21.\u003c/li\u003e\n \u003cli\u003eM\u0026uuml;ller S, K\u0026ouml;hler F, Hendricks A, Maih\u0026ouml;fer C, Makowiec F. Brain metastases from colorectal cancer: a systematic review and meta-analysis to establish a guideline for daily treatment. \u003cem\u003eCancers (Basel)\u003c/em\u003e. 2021;13(4):900.\u003c/li\u003e\n \u003cli\u003eMjahed RB, Astaras C, Roth A, Koessler T. Where are we now and where might we be headed in understanding and managing brain metastases in colorectal cancer patients? \u003cem\u003eCurr Treat Options Oncol\u003c/em\u003e. 2022;23(7):980-1000. doi:10.1007/s11864-022-00982-0.\u003c/li\u003e\n \u003cli\u003eChen Q, He L, Li Y, Zuo C, Li M, Wu X, et al. Risk factors on the incidence and prognostic effects of colorectal cancer with brain metastasis: a SEER-based study. \u003cem\u003eFront Oncol\u003c/em\u003e. 2022;12:758681. doi:10.3389/fonc.2022.758681.\u003c/li\u003e\n \u003cli\u003eBatson OV. The function of the vertebral veins and their role in the spread of metastases. \u003cem\u003eAnn Surg\u003c/em\u003e. 1940;112(1):138-49.\u003c/li\u003e\n \u003cli\u003eSchroeder HW, Hall LT. Molecular imaging of brain metastases with positron emission tomography. In: \u003cem\u003eMetastasis: Clinical and Biological Perspectives\u003c/em\u003e. Exon Publishing; 2022. p. 233-49.\u003c/li\u003e\n \u003cli\u003eChang Y, Wong CE, Lee PH, Ng DC, Cheung SH. Survival outcome of surgical resection versus radiotherapy in brain metastasis from colorectal cancer: a meta-analysis. \u003cem\u003eFront Med (Lausanne)\u003c/em\u003e. 2022;9:768896.\u003c/li\u003e\n \u003cli\u003eNavarria P, Mazzarella A, Clerici E, Ascolese AM, Franzese C, Tomatis S, et al. Stereotactic radiosurgery for brain metastases from colorectal cancer: a multicentre study. \u003cem\u003eActa Oncol\u003c/em\u003e. 2020;59(9):1118-26.\u003c/li\u003e\n \u003cli\u003eChernov M, Hayashi M. Radiosurgery for brain metastases of colorectal cancer. \u003cem\u003eBr J Radiol\u003c/em\u003e. 2022;95(1136):20210179. doi:10.1259/bjr.20210179.\u003c/li\u003e\n \u003cli\u003eBrown PD, Ballman KV, Cerhan JH, Anderson SK, Carrero XW, Whitton AC, et al. 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EANO-ESMO Clinical Practice Guidelines for diagnosis, treatment and follow-up of patients with brain metastasis from solid tumours. \u003cem\u003eAnn Oncol\u003c/em\u003e. 2021;32(11):1332-47. doi:10.1016/j.annonc.2021.07.016.\u003c/li\u003e\n \u003cli\u003eLi Y, Wu J, Liu F, Shao X, Liang X, Zhang F, et al. Single-fraction SRS and multiple-fraction SRT for brain metastases from colorectal cancer. \u003cem\u003eFront Oncol\u003c/em\u003e. 2022;12:1060570. doi:10.3389/fonc.2022.1060570.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":false,"highlight":"","institution":"Department of Nuclear Medicine, Faculty of Medicine, Samsun University, Samsun, Türkiye","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"colon cancer, solitary brain metastasis, F18 FDG PET/CT","lastPublishedDoi":"10.21203/rs.3.rs-6812456/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6812456/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cstrong\u003eBackground:\u003c/strong\u003e Brain metastasis (BM) is observed in approximately 1–4% of cases involving metastatic colon cancer and is almost invariably associated with extracranial dissemination. The occurrence of isolated intracranial disease in the absence of systemic metastases is, therefore, exceedingly rare.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCase presentation:\u003c/strong\u003e We report a 74 year-old female who presented with new-onset focal seizures 18 months after curative surgery for stage IIIC sigmoid adenocarcinoma. The F18 FDG PET/CT scan revealed increased F18 FDG uptake in an 18x19 mm hyperdense lesion located in the right temporal lobe, accompanied by a substantial edematous region in the surrounding area (SUV max:8.0) but no abnormal F18 FDG accumulation elsewhere, confirming isolated BM. Brain MRI revealed a 28x30 mm contrast-enhancing lesion in the right temporal lobe with vasogenic edema. The patient underwent gross-total resection followed by adjuvant stereotactic radiosurgery (SRS, 18 Gy single fraction). Histopathology showed metastatic moderately-differentiated colon adenocarcinoma (CK20+, CDX-2+, CK7+, P53+). Post-operative capecitabine plus bevacizumab was given for six cycles. At 12-month follow-up the patient remains disease-free on surveillance MRI and F18 PET/CT.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConclusion:\u003c/strong\u003e This case illustrates the diagnostic value of F18 FDG PET/CT in excluding extracranial disease and supports an aggressive local-therapy strategy (surgery ± SRS) for solitary kolon adenocarsinoma BM, which may confer prolonged survival.\u003c/p\u003e","manuscriptTitle":"Detection of an Isolated Solitary Brain Metastasis from Colon Adenocarcinoma via 18F-FDG PET/CT: A Rare Case and Its Multimodal Management","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-06-09 08:47:32","doi":"10.21203/rs.3.rs-6812456/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"24501818-d291-40f9-992e-894bf64aacac","owner":[],"postedDate":"June 9th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[{"id":49520946,"name":"Nuclear Medicine \u0026 Medical Imaging"}],"tags":[],"updatedAt":"2025-07-17T22:47:55+00:00","versionOfRecord":{"articleIdentity":"rs-6812456","link":"https://doi.org/10.5455/TheJODTi.1606.2404","journal":{"identity":"the-journal-of-diagnostic-and-theranostic-imaging","isVorOnly":true,"title":"The Journal of Diagnostic and Theranostic Imaging"},"publishedOn":"2025-06-27 00:00:00","publishedOnDateReadable":"June 27th, 2025"},"versionCreatedAt":"2025-06-09 08:47:32","video":"","vorDoi":"10.5455/TheJODTi.1606.2404","vorDoiUrl":"https://doi.org/10.5455/TheJODTi.1606.2404","workflowStages":[]},"version":"v1","identity":"rs-6812456","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6812456","identity":"rs-6812456","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}