Effect of the duration of the capecitabine regimen following colon cancer surgery in an elderly population: a retrospective cohort study

BACKGROUND: Only 50–70% of elderly colon cancer patients could complete the recommended 6 months of postoperative chemotherapy. It is unknown whether a shorter duration of postoperative capecitabine-alone chemotherapy would compromise survival. We thus conducted this study to analyze the association between postoperative chemotherapy duration of a capecitabine-alone regimen and cancer-specific survival (CSS) and disease-free survival (DFS) of surgery-treated elderly colon cancer patients. METHODS: We performed a retrospective cohort study of surgically treated stage III and high-risk stage II colon cancer patients aged ≥ 70 treated at two medical centers. Cox proportional hazard regression models were utilized to calculate crude and adjusted hazard ratios (HRs). The nonlinear relationship between postoperative chemotherapy duration and survival was analyzed through restricted cubic spline regression analysis, and the threshold effect was calculated by the two-piecewise Cox proportional hazard model. RESULTS: A total of 1217 surgery-treated colon cancer patients between August 1, 2013, and September 1, 2019, were reviewed, and 257 stage III and high-risk stage II patients aged ≥ 70 were enrolled. Postoperative chemotherapy with capecitabine was administered to 114 patients, and 143 patients only received surgery. As the duration of chemotherapy increased by 1 week, the risk of cancer-specific death was reduced by 11% (HR = 0.89, 95% confidence interval (CI) 0.82–0.96), and the risk of recurrence was reduced by 10% (HR = 0.90, 0.82–0.96). Nonlinearity exploration suggested a threshold effect of capecitabine duration on CSS in stage III disease. The HR for death was 0.79 (95% CI, 0.68–0.92) with duration ≤ 16 weeks and 1.34 (95% CI, 0.91–1.97) with duration > 16 weeks. CONCLUSIONS: The postoperative capecitabine duration was significantly associated with a decrease in death risk and recurrence risk in elderly colon cancer patients. However, the threshold effect of capecitabine duration on survival suggests that short-term chemotherapy may improve survival in elderly stage III colon cancer patients.