Oncologic Outcomes and Adjuvant Chemotherapy Use in Early- Versus Late-Onset Colon Cancer: A Propensity Score–Matched Analysis

BACKGROUND: The incidence of early-onset colon cancer is increasing, and younger patients are often treated more intensively on the assumption of worse prognosis. OBJECTIVE: To determine whether early-onset presentation is independently associated with prognosis, and to compare adjuvant chemotherapy use and effect between age groups. DESIGN: Retrospective cohort study with 1:3 propensity score matching and exact matching on stage. SETTINGS: A single tertiary referral center. PATIENTS: Patients who underwent curative resection for stage I to III colon cancer between 2012 and 2020. Early onset was defined as diagnosis before age 50. INTERVENTIONS: Curative resection with or without adjuvant chemotherapy. MAIN OUTCOME MEASURES: Recurrence-free survival was the primary outcome; overall survival and adjuvant chemotherapy use and effect were secondary. RESULTS: Of 5,032 patients, 749 (14.9%) had early-onset disease; 656 were matched to 1,968 late-onset patients. Five-year recurrence-free survival did not differ between the groups (88.0 vs 86.1%; p = 0.09), and early onset was not independently associated with recurrence or death after adjustment for tumor factors and adjuvant chemotherapy, both in the matched (adjusted hazard ratio 0.85; 95% confidence interval 0.66-1.10) and entire cohort (0.79; 0.62-1.00). Among early-onset patients, recurrence-free survival was independently associated with T4 classification, nodal category, and poor differentiation. Nonetheless, early-onset patients received adjuvant chemotherapy more often (60.2 vs 53.5%; p = 0.003), including in low-risk Stage II disease (37.7 vs 14.3%; p < 0.001). LIMITATIONS: Retrospective single-center design with potential residual confounding; few early-onset patients did not receive chemotherapy. CONCLUSIONS: Early-onset presentation was not significantly associated with recurrence-free survival after multivariable adjustment in the matched cohort. Early-onset patients nonetheless received adjuvant chemotherapy more frequently and more intensively, including in low-risk Stage II disease. The observational design and the small number of untreated early-onset patients limit conclusions regarding age-specific chemotherapy benefit. See Video Abstract.