Comparing tumour site and overall survival in colon v. rectal cancer in a longitudinal cohort study in Johannesburg, South Africa

Abstract

Background. Colorectal cancer (CRC) incidence is increasing globally, with disproportionately high mortality in low- and middle-income countries. Although colon and rectal cancers are often grouped together, anatomical, molecular and clinical differences suggest they may be distinct entities, warranting unique work-up, management and diagnosis. Data from sub-Saharan Africa comparing clinical presentation and mortality outcomes among those with colon and rectal cancer remain limited. This study aimed to address this knowledge gap. Objectives. To compare the clinicopathological features, associated risk factors and overall survival (OS) of patients with colon and rectal cancers in the cohort from the Colorectal Cancer in South Africa Study in Johannesburg, South Africa (SA). Methods. The cohort eligible for inclusion in this study comprised 325 patients, recruited from 2016 to 2019, with follow-up to January 2023. Sociodemographic, clinical, treatment and OS data were analysed. Comparison by tumour location was made using t-tests and ANOVA. Cox proportional hazards regression models assessed associations with OS. Kaplan-Meier analysis was used for survival estimation. Results. Rectal cancers accounted for 52.3% of cases, right-sided colon cancers 26.2% and left-sided colon cancers 21.5%. When comparing those who presented with colon v. rectal cancers, no significant differences were observed in self-reported ethnicity, socioeconomic status (SES), family history of cancer, tobacco use, body mass index, or presence of comorbidities. Alcohol use was more common among those with colon cancer (p=0.035), and treatment differed significantly by tumour site (p<0.0001). Male sex (hazard ratio (HR) 1.81, 95% confidence interval (CI) 1.25 - 2.61, p=0.0017), low SES (HR 3.24, CI 1.86 - 5.65, p<0.0001) and distant disease at presentation (HR 3.85, CI 2.26 - 6.57, p<0.0001) were most strongly associated with poorer OS. The tumour site had no impact on OS. Conclusion. In this SA cohort of patients with CRC, tumour site did not affect overall survival. However, male sex, advanced stage at diagnosis and low socioeconomic status were associated with poorer OS.