Efficacy of Adjuvant Chemotherapy for T1-2 Stage III Colorectal Cancer

Background/Objectives: This study aimed to assess the efficacy of adjuvant chemotherapy for T1-2 stage III colorectal cancer, a disease with a low recurrence rate. Methods: The efficacies of fluorouracil-based adjuvant chemotherapy (5FU group) and oxaliplatin-based adjuvant chemotherapy (L-OHP group) were assessed and compared with that of surgery alone (surgery group) using data from seven clinical trials conducted by the Japanese Foundation for Multidisciplinary Treatment of Cancer. Propensity score matching was used to compare the three groups. Direct-adjusted survival curves were delineated with consideration of treatment periods. Results: A total of 604 patients with T1-2 stage III colorectal cancer were identified. After adjusting for the patient factors, the hazard ratio of relapse-free survival (RFS) was 0.79 (95% confidence interval (CI): 0.13–4.65, p = 0.79) and 0.64 (95% CI: 0.06–6.40, p = 0.70) in the 5FU and L-OHP groups, respectively. Adjusted 5-year RFS rate was 82.8% (95% CI: 67.2–100%), 86.2% (95% CI: 74.2–100%), and 88.6% (95% CI: 74.0–100%) in the surgery, 5-FU, and L-OHP groups, respectively. Overall and disease-specific survival showed similar trends without significant differences. Conclusions: No significant improvement in prognosis was observed after adjuvant chemotherapy. The potential improvement in the 5-year RFS after adjuvant chemotherapy for resected T1-2 stage III colorectal cancer should be balanced with patient factors and adverse events.