Survival Rates of Patients Diagnosed with Colorectal Cancer in Costa Rica (2020-2021): A Retrospective Cohort Study at the Centro de Detección Temprana de Cáncer Gástrico

Objective: To evaluate the impact of tumor location, TNM stage, and treatment modalities on survival among colorectal cancer (CRC) patients in Costa Rica (CR). Design: Retrospective cohort study. Setting: Centro de Detección Temprana de Cáncer Gástrico (CDTCG), Cartago, CR. Participants: 101 patients diagnosed with CRC between January 2020 and December 2021, identified from institutional records. Methods: Demographic, clinical, histopathological, and treatment data were extracted and analyzed. Survival was assessed using Kaplan–Meier and Cox proportional hazards models, including time-dependent covariates to evaluate variations in treatment effects over time. Results: The mean age was 62.5 years; 53.5% were male. Rectal cancer was most frequent (45.5%), and 45% presented with regional disease. FIT-based diagnosis was associated with improved survival (HR: 0.24, p = 0.001). Left-sided tumors showed better prognosis than right-sided (HR: 0.38, p = 0.03). Surgical intervention significantly reduced mortality, particularly in regional-stage disease. Adjuvant therapy initially improved survival (HR: 0.07, p = 0.006) but its benefit declined over time (HR: 4.82, p < 0.001). FOLFOX/XELOX was associated with worse survival, likely reflecting advanced-stage selection bias. Conclusions: Early detection, tumor location, and timely surgical intervention are key determinants of CRC survival in CR. Time-dependent analyses highlight the need for ongoing monitoring of treatment effects to optimize long-term outcomes.