Clinicopathological features and survival outcomes of mucinous versus non-mucinous colon adenocarcinoma: a retrospective cohort study from a tertiary cancer centre in South India

Background: Mucinous adenocarcinoma (MAC) is a distinct histological subtype of colorectal cancer whose prognostic significance remains debated, and data from Indian patients are scarce. We compared the clinicopathological profile and overall survival (OS) of mucinous and non-mucinous adenocarcinoma (NMAC) of the colon treated at a tertiary cancer centre in South India. Material and Methods: This retrospective cohort study included consecutive patients with histologically confirmed colon adenocarcinoma diagnosed between December 2015 and February 2021 and treated at the Department of Medical Oncology, Vydehi Institute of Medical Sciences and Research Centre, Bangalore. Baseline characteristics were compared with Fisher's exact and Mann–Whitney tests. OS was estimated by the Kaplan–Meier method, compared with the log-rank test, and analysed with Cox proportional hazards regression. Results: Of 45 patients (median age 50 years; 55.6% stage IV), 10 (22.2%) had MAC. Stage distribution was similar between groups (stage IV 50.0% vs 57.1%; p = 1.000). MAC showed non-significant trends towards female sex (62.5% vs 25.0% of patients with recorded sex; p = 0.086), right-sided location (77.8% vs 57.1%) and younger age (median 48 vs 52 years). At a median follow-up of 41.1 months, 17 patients had died. Median OS was 11.7 months for MAC and not reached for NMAC (log-rank p = 0.073); 3-year OS was 45.7% vs 64.5%. After adjustment for stage, MAC was independently associated with inferior OS (hazard ratio [HR] 3.46 (1.25–9.61); p = 0.017), a finding unchanged in a stage-stratified model (HR 3.55 (1.28–9.90)). The difference was most marked in stage IV disease (median OS 6.6 vs 33.5 months; p = 0.018). Conclusion: MAC accounted for more than one in five colon cancers in this South Indian cohort and was associated with poorer stage-adjusted survival, particularly in metastatic disease. Given the small sample, these findings are hypothesis-generating and support larger multicentre Indian studies incorporating mismatch-repair and RAS/BRAF profiling.

Keywords: Colon Cancer, Mucinous Adenocarcinoma, Histological Subtype, Overall Survival, Prognosis; India.