A Comparative Dosimetric Baseline for Right-Sided Breast Cancer: Are We Ignoring the Lung in the Pursuit of Heart Sparing? A Multi-Dimensional Analysis of Laterality, Anatomical Asymmetry, and Organ-at-Risk Prioritization in Modern Radiotherapy

A Comparative Dosimetric Baseline for Right-Sided Breast Cancer: Are We Ignoring the Lung in the Pursuit of Heart Sparing? A Multi-Dimensional Analysis of Laterality, Anatomical Asymmetry, and Organ-at-Risk Prioritization in Modern Radiotherapy | 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 A Comparative Dosimetric Baseline for Right-Sided Breast Cancer: Are We Ignoring the Lung in the Pursuit of Heart Sparing? A Multi-Dimensional Analysis of Laterality, Anatomical Asymmetry, and Organ-at-Risk Prioritization in Modern Radiotherapy Ashmita Ghosh This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8882115/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Purpose: The era of modern breast radiotherapy has been defined by "Cardiac Sparing," driven by the known cardiotoxicity of left-sided irradiation. This focus has led to the widespread adoption of Deep Inspiratory Breath Hold (DIBH) and intensity-modulated techniques for left-sided breast cancer (LSBC). However, a critical question remains: In the absence of a cardiac constraint, are Right-Sided Breast Cancer (RSBC) patients subjected to suboptimal lung dosimetry due to "benign planning neglect"? This study aims to establish a rigorous dosimetric benchmark for RSBC and compare it with LSBC to determine if lung sparing is being compromised when the heart is not at risk. Methods: We conducted a prospective comparative analysis of 150 patients (Right=75, Left=75) treated at a tertiary oncology center. To capture the nuance of anatomical asymmetry, the dataset was expanded to 100 high-dimensional variables, including cardiac contact distances, lung volume differentials, and tangential field geometry. All patients were treated with 40 Gy in 15 fractions. We utilized propensity score matching to control for PTV volume and BMI. The primary endpoints were Ipsilateral Mean Lung Dose (MLD) and V20; the secondary endpoint was the "Dosimetric Efficiency Ratio" (DER), defined as the ratio of PTV coverage to OAR integral dose. Results: Preliminary analysis reveals a paradox: Despite the lack of cardiac constraints, RSBC patients exhibited a mean MLD of 9.8 Gy compared to 8.4 Gy in the LSBC cohort (p < 0.05). This 1.4 Gy differential suggests that the rigorous optimization constraints applied to protect the heart in LSBC have a beneficial "bystander effect" on the left lung, which is absent in RSBC planning. Furthermore, DIBH usage was non-existent in the RSBC group, despite its potential to reduce lung density and dose. Conclusion: The pursuit of heart sparing in LSBC has inadvertently created a disparity in lung protection. Right-sided patients, considered "anatomically safe" from cardiac events, are receiving higher pulmonary doses. This study calls for a re-evaluation of planning priorities, advocating for the application of "Heart-Level Constraints" to the Right Lung to establish a true universal standard of care. Oncology Dosimetric analysis right sided breast cancer anatomical asymmetry MHD mean lung dose total lung capacity contralateral lung volume DIBH pulmonary toxicity. Full Text Additional Declarations The authors declare no competing interests. Cite Share Download PDF Status: Posted 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. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. 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-8882115","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":591449415,"identity":"abdeaf79-75d0-4e5a-a75b-1e684a5a64fe","order_by":0,"name":"Ashmita Ghosh","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA70lEQVRIiWNgGAWjYFACHgaGBAYGO3725oMPQFw+4rQkMCRL9hxLNgBx2YjSArSGccONHDMJEJ+gFv7+s0c3PPxhx8xwI8Gs8muOnQwbA/PDRzfwaJG4kZd2IyEhmY+x50HabdltyUCHsRkb5+Cz5gaPGVALMzMze8Kx25LbmIFaeNik8WmRP38GpKWesY0hsa1Ycls9YS0GB3JAWg4z9nAkszF+3HaYsBbDGyAtaceTJXiOMUszbjvOw8ZMwC9yQIfd/GFTbWd/vP/jx5/bqu2BcfrwMV7vIwNmHjBJrHIQYPxBiupRMApGwSgYMQAAmvFJP5aFIsMAAAAASUVORK5CYII=","orcid":"https://orcid.org/0009-0008-5550-2960","institution":"Institute of Post Graduate Medical Education and Research","correspondingAuthor":true,"prefix":"","firstName":"Ashmita","middleName":"","lastName":"Ghosh","suffix":""}],"badges":[],"createdAt":"2026-02-14 18:55:53","currentVersionCode":1,"declarations":{"humanSubjects":true,"vertebrateSubjects":false,"conflictsOfInterestStatement":false,"humanSubjectEthicalGuidelines":true,"humanSubjectConsent":true,"humanSubjectClinicalTrial":false,"humanSubjectCaseReport":false,"vertebrateSubjectEthicalGuidelines":false},"doi":"10.21203/rs.3.rs-8882115/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-8882115/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":102962617,"identity":"2f51903c-549f-45eb-9f8e-308a478c24a5","added_by":"auto","created_at":"2026-02-19 04:10:10","extension":"pdf","order_by":1,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":364486,"visible":true,"origin":"","legend":"","description":"","filename":"AComparativeDosimetricBaselineforRight.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8882115/v1_covered_16132075-0f37-48e0-ae2f-5f620d1b8036.pdf"}],"financialInterests":"The authors declare no competing interests.","formattedTitle":"\u003cp\u003e\u003cstrong\u003eA Comparative Dosimetric Baseline for Right-Sided Breast Cancer: Are We Ignoring the Lung in the Pursuit of Heart Sparing?\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eA Multi-Dimensional Analysis of Laterality, Anatomical Asymmetry, and Organ-at-Risk Prioritization in Modern Radiotherapy\u003c/strong\u003e\u003c/p\u003e","fulltext":[],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":false,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":true,"highlight":"","institution":"Institute of Post Graduate Medical Education and Research","isAcceptedByJournal":false,"isAuthorSuppliedPdf":true,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":true,"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":"Dosimetric analysis, right sided breast cancer, anatomical asymmetry, MHD, mean lung dose, total lung capacity, contralateral lung volume, DIBH, pulmonary toxicity.","lastPublishedDoi":"10.21203/rs.3.rs-8882115/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8882115/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003ePurpose: The era of modern breast radiotherapy has been defined by \"Cardiac Sparing,\" driven by the known cardiotoxicity of left-sided irradiation. This focus has led to the widespread adoption of Deep Inspiratory Breath Hold (DIBH) and intensity-modulated techniques for left-sided breast cancer (LSBC). However, a critical question remains: In the absence of a cardiac constraint, are Right-Sided Breast Cancer (RSBC) patients subjected to suboptimal lung dosimetry due to \"benign planning neglect\"? This study aims to establish a rigorous dosimetric benchmark for RSBC and compare it with LSBC to determine if lung sparing is being compromised when the heart is not at risk.\u003c/p\u003e\n\u003cp\u003eMethods: We conducted a prospective comparative analysis of 150 patients (Right=75, Left=75) treated at a tertiary oncology center. To capture the nuance of anatomical asymmetry, the dataset was expanded to 100 high-dimensional variables, including cardiac contact distances, lung volume differentials, and tangential field geometry. All patients were treated with 40 Gy in 15 fractions. We utilized propensity score matching to control for PTV volume and BMI. The primary endpoints were Ipsilateral Mean Lung Dose (MLD) and V20; the secondary endpoint was the \"Dosimetric Efficiency Ratio\" (DER), defined as the ratio of PTV coverage to OAR integral dose.\u003c/p\u003e\n\u003cp\u003eResults: Preliminary analysis reveals a paradox: Despite the lack of cardiac constraints, RSBC patients exhibited a mean MLD of 9.8 Gy compared to 8.4 Gy in the LSBC cohort (p \u0026lt; 0.05). This 1.4 Gy differential suggests that the rigorous optimization constraints applied to protect the heart in LSBC have a beneficial \"bystander effect\" on the left lung, which is absent in RSBC planning. Furthermore, DIBH usage was non-existent in the RSBC group, despite its potential to reduce lung density and dose.\u003c/p\u003e\n\u003cp\u003eConclusion: The pursuit of heart sparing in LSBC has inadvertently created a disparity in lung protection. Right-sided patients, considered \"anatomically safe\" from cardiac events, are receiving higher pulmonary doses. This study calls for a re-evaluation of planning priorities, advocating for the application of \"Heart-Level Constraints\" to the Right Lung to establish a true universal standard of care.\u003c/p\u003e","manuscriptTitle":"A Comparative Dosimetric Baseline for Right-Sided Breast Cancer: Are We Ignoring the Lung in the Pursuit of Heart Sparing?\nA Multi-Dimensional Analysis of Laterality, Anatomical Asymmetry, and Organ-at-Risk Prioritization in Modern Radiotherapy","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-02-17 10:30:44","doi":"10.21203/rs.3.rs-8882115/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":"5dd1dfb2-6e6b-4934-87e9-6bf506e83ba1","owner":[],"postedDate":"February 17th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":62940994,"name":"Oncology"}],"tags":[],"updatedAt":"2026-02-17T10:30:44+00:00","versionOfRecord":[],"versionCreatedAt":"2026-02-17 10:30:44","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8882115","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8882115","identity":"rs-8882115","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}