Age cut-off for oxaliplatin efficacy in stage II/III colorectal cancer

초록

Background: Colorectal cancer is a major cause of cancer deaths, with rising incidence in older adults. While oxaliplatin-based adjuvant therapy is standard for stage II/III disease, its value in older patients remains uncertain. Using national health insurance data, we investigated the optimal age threshold for the survival benefit of adding oxaliplatin to fluoropyrimidine-based adjuvant chemotherapy in stage II/III colorectal cancer. Methods: We conducted a population-based retrospective study using data from Korea’s Health Insurance Review and Assessment Service (HIRA) National Quality Assessment program. Patients who underwent curative resection for stage II/III colon cancer between 2014 and 2016, followed by adjuvant chemotherapy, were included. After applying eligibility criteria and exclusions, 8,561 patients remained for final analysis in 2024. Two treatment groups were compared: oxaliplatin-based adjuvant chemotherapy (CAPOX, FOLFOX, or mFOLFOX) versus fluoropyrimidine-only regimens (fluorouracil plus leucovorin or capecitabine). The primary outcome was overall survival, which was assessed using Cox proportional hazards regression and propensity score matching. Age thresholds (60–80 years) were systematically examined to determine the optimal cut-off for oxaliplatin benefit. Results: Of 8,561 patients (mean age 63.7 years, 54.2% male), 2,913 had stage II and 5,648 had stage III cancer. In stage II, oxaliplatin offered no survival benefit at any age threshold. In stage III, oxaliplatin significantly improved survival up to age 70 (adjusted hazard ratio [aHR], 0.59; 95% CI, 0.46–0.77; P<0.001), with a 5-year overall survival of 84.8% versus 78.1% (P=0.003). Beyond age 70, oxaliplatin showed no significant benefit (aHR, 0.85; 95% CI, 0.67–1.07; P=0.182). For patients ≤70 years, oxaliplatin use did not significantly increase discontinuation (adjusted odds ratio [aOR], 1.12; 95% CI, 0.88–1.42; P=0.326), but it did in those >70 (aOR, 1.53; 95% CI, 1.17–2.01; P=0.002). Conclusions: In this large cohort, oxaliplatin improved survival in stage III patients ≤70 but not in older individuals, with no benefit in stage II. Oxaliplatin correlated with higher discontinuation in those >70, highlighting the need for tailored strategies.