A Clinicopathologic, Molecular, and Prognostic Comparison Between Early- and Late-Onset Colorectal Cancer in Korea: A Single-Center Retrospective Cohort Study.

: The incidence of early-onset colorectal cancer (EO-CRC), diagnosed before age 50, is increasing worldwide; however, comparative data between patients with EO-CRC and late-onset colorectal cancer (LO-CRC) in Asian populations remain limited. We compared the clinicopathological, molecular, and prognostic characteristics of EO-CRC and LO-CRC in a tertiary-center cohort. : This retrospective cohort study included patients with histologically confirmed colorectal adenocarcinoma treated at a single tertiary referral center between January 2011 and December 2024. Patients were classified as having EO-CRC (<50 years) or LO-CRC (≥50 years). Demographic and lifestyle factors, clinicopathological characteristics, laboratory findings including blood tests and tumor markers, and molecular profiles such as microsatellite instability (MSI) status and selected gene mutations were compared. Overall survival and associated prognostic factors were evaluated using multivariate analysis. : Among 1383 patients, 104 had EO-CRC and 1279 had LO-CRC. Patients with EO-CRC reported smoking and alcohol consumption more frequently, had fewer comorbidities, and showed a higher prevalence of distal tumors, particularly rectal cancer, with a lower T stage. Nodal and distant metastatic stages were comparable between the groups, with no difference in the proportion of stage IV disease. Laboratory parameters, tumor marker levels, MSI status, and other available molecular markers were not significantly different. Overall survival did not differ significantly between EO-CRC and LO-CRC. : EO-CRC exhibited distinct clinical features; however, molecular characteristics and survival outcomes were similar to those of LO-CRC. Prognosis is primarily determined by disease stage rather than the age at diagnosis, supporting the importance of early detection strategies in high-risk populations.