Survival of Colon Cancer in a Population-Based Cohort Study - A Comprehensive Analysis of Location of the Primary Tumor

Q: What is the main research question of the study?

The study examines how the location (left versus right sidedness) of the primary colon tumor affects survival, including within subgroups defined by tumor biomarkers.

Q: How were left- and right-sided colon cancers defined?

They were classified using ICD-O codes: right-sided tumors correspond to C18.0 and C18.2–18.4, while left-sided tumors correspond to C18.5–18.7.

Q: What does the study find about 5-year net survival by sidedness?

Left-sided colon cancer shows higher 5-year net survival than right-sided colon cancer (66% vs. 59%), and multivariable analysis indicates reduced 5-year mortality for left-sided tumors.

Sep 22, 2026

Upload by OmBimo

Disparities in survival between left- versus right-sided colon cancer have been reported, and this study evaluates how tumor sidedness influences survival across biomarker subgroups. Using Geneva Cancer Registry data, 3503 colon cancer cases diagnosed from 1985 to 2013 were analyzed, comparing right- and left-sided tumors by ICD-O codes. Five-year net survival was estimated with the Pohar-Perme method and assessed via flexible hazard models adjusted for patient, tumor, and treatment factors.

LanguageEnglish

CategoryResearch & Report

FormatPDF

Pages11

Reading Time28 min

AccessFree to download

Introduction

Colon cancer sidedness and molecular phenotypes

Treatment response and survival trends

Cancer Medicine | RESEARCH ARTICLE OPEN ACCESS
Survival of Colon Cancer in a Population-Based Cohort Study: A Comprehensive Analysis of Location of the Primary Tumor
Pauline Brindel1 | Evelyne Fournier1 | Pierre Olivier Chappuis2,3 | Thomas McKee4 | Mario Kreutzfeldt5 | Giacomo Puppa4 | Johan Ferrari4 | Jakob Nikolas Kather6,7,8,9 | Elisabetta Rapiti1 | Simone Benhamou10
1Geneva Cancer Registry, Institute of Global Health, University of Geneva, Geneva, Switzerland | 2Oncogenetics Unit, Division of Precision Oncology, Geneva University Hospitals, Geneva, Switzerland | 3Division of Genetic Medicine, Geneva University Hospitals, Geneva, Switzerland | 4Department of Clinical Pathology, Geneva University Hospitals, Geneva, Switzerland | 5Department of Pathology and Immunology, University of Geneva, Geneva, Switzerland | 6Else Kroener Fresenius Center for Digital Health, Faculty of Medicine and University Hospital Carl Gustav Carus, TUD Dresden University of Technology, Dresden, Germany | 7Department of Medicine I, Faculty of Medicine and University Hospital Carl Gustav Carus, TUD Dresden University of Technology, Dresden, Germany | 8Medical Oncology, National Center for Tumor Diseases (NCT), University Hospital Heidelberg, Heidelberg, Germany | 9Pathology & Data Analytics, Leeds Institute of Medical Research at St James's, University of Leeds, Leeds, UK | 10INSERM Unit 1018, Research Center on Epidemiology and Population Health, Villejuif, Île de France, France
Correspondence: Pauline Brindel ([pauline.brindel@unige.ch](pauline.brindel@unige.ch))
Received: 11 April 2025 | Revised: 22 December 2025 | Accepted: 26 June 2026
Keywords: biomarkers | colorectal cancer | molecular oncology | registry | survival | | --- | | ABSTRACT
Disparities in survival between left-versus right-sided colon cancer have been reported. We studied the role of sidedness on survival of colon cancer across tumor biomarkers subgroups in a population-based cohort established using the Geneva Cancer Registry database. Our study included 3503 colon cancer cases diagnosed between 1985 and 2013. Right-sided colon cancers (ICD-O codes C18.0, C18.2–18.4) and left-sided colon cancers (ICD-O codes C18.5–18.7) were compared. Five-year net survival was estimated using the Pohar-Perme estimator. Flexible hazard models evaluated the association of survival with sidedness adjusted for patient, tumor, and treatment characteristics. Left-sided colon cancers were more frequent than right-sided colon cancers (53% vs. 47%) . Right-sided colon cancer cases were older and more often women, less frequently of stage I or well differentiated. Left-sided colon cancer had a higher 5-year net survival than right-sided colon cancer (66% vs. 59%, p < 0.001) . In a multivariable model, patients with a left-sided tumor had a 25% reduction in 5-year mortality compared with right-sided tumors (excess hazard ratio [eHR]: 0.75, 95% confidence interval [CI]: 0.63–0.89, p = 0.001) . This association remained significant only among stage IV while not among stages I-III. Among a subgroup of 2438 cases, stratification on tumor molecular biomarkers confirmed the better prognosis of left-sided colon cancer versus right-sided colon cancer among microsatellite stable (MSS) tumors, tumors with BRAF wild-type (BRAFwt), and iCMS2 tumors. This study shows the importance of sidedness for prognosis and treatment considerations in addition to tumor biomarkers. Further research is needed to assess the molecular mechanisms underlying these differences between left and right colon cancer to address the prognostic gap. | | | | Abbreviations: ANOVA, analysis of variance; CI, confidence interval; CMS1, consensus molecular subtype 1; CMS2, consensus molecular subtype 2; CMS3, consensus molecular subtype 3; EGFR, epidermal growth factor receptor; eHR, excess hazard ratio; ESMO, European Society for Medical Oncology; HR, hazard ratio; ICD-O, International Classification of Disease for O

FAQs

What is the main research question of the study?

The study examines how the location (left versus right sidedness) of the primary colon tumor affects survival, including within subgroups defined by tumor biomarkers.

How were left- and right-sided colon cancers defined?

They were classified using ICD-O codes: right-sided tumors correspond to C18.0 and C18.2–18.4, while left-sided tumors correspond to C18.5–18.7.

What does the study find about 5-year net survival by sidedness?

Left-sided colon cancer shows higher 5-year net survival than right-sided colon cancer (66% vs. 59%), and multivariable analysis indicates reduced 5-year mortality for left-sided tumors.

Sep 22, 2026

Upload by OmBimo