Survival outcomes in right-sided versus left-sided colon cancer in a South Asian population- a retrospective cohort study

Introduction: Large bowel cancer is among the most common cancers in Sri Lanka, ranking second in men and third in women. Rectal and colon cancers behave differently. It is postulated that right colon cancers (RCC) have a poorer survival due to poor response to adjuvant therapy and different molecular
properties. This study evaluated survival outcomes between left colon cancers (LCC) and RCC in a Sri Lankan cohort.
Methodology: A retrospective cohort study was conducted, including 785 adult patients who underwent curative resection for colon cancer at a tertiary care centre from 1997 to August 2025. Patients were followed up and entered into a database. Five-year overall survival (OS) and disease-free survival (DFS) were compared between LCC and RCC. Cox proportional hazards models were used to assess prognostic factors. Propensity score matching based on age and sex was performed to reduce baseline differences.
Results: LCC accounted for 84.5% of cases, while RCC accounted for 15.2%. Median age at diagnosis was 60 years, and 24.1% had young-onset disease. No significant difference was observed between LCC and RCC in 5-year OS (43.2% vs. 40.0%, p=0.783) or DFS (p=0.292). Similar results were observed in propensity score-matched analysis. Survival was unaffected by sex or preoperative albumin but was influenced by age, lymph node status, and tumour stage (pT).
Conclusion: A lower proportion of RCC was observed compared with the West. Tumour sidedness was not associated with survival outcomes in Sri Lankan cohort. Larger multicentre studies are required to evaluate the significance of tumour location in South Asian populations.