Does 1 year adjuvant chemotherapy with oral 5-FUs in colon cancer reduce the peak of recurrence in 1 year and provide long-term OS benefit?

The objective of our study was to clarify the characteristics of survival and hazard function in patients who received adjuvant chemotherapy after surgery for colon cancer. The data of 2848 patients with curatively resected colon cancer were analyzed; we used the patient data provided by the Japanese Foundation for Multidisciplinary Treatment for Cancer in three trials, namely, JFMC7-1 (n = 869), JFMC7-2 (n = 978) and JFMC15 (n = 1001). The total number of events were 605 (overall survival) and 724 (disease-free survival). The disease-free survival events consisted of 117 cases of death and 607 cases of disease recurrences. Logrank test showed a borderline significant difference in both overall survival (P = 0.0452) and disease-free survival (P = 0.0462). The 5 year overall survival proportion was 0.769 (control) and 0.802 (treated), and the absolute drug effect was 3.3%. The difference between the 5 year disease-free survival proportion (0.728 [control] and 0.760 [drug]) was 3.2%, which is almost similar to the result of overall survival. The disease-free survival curve of the treated group differed from that of the control group after 1 year, whereas the overall survival curve of the treated group became distinct from that of the control group after 2 years. The hazard rate plots indicated the possibility that 1 year adjuvant chemotherapy with oral 5-fluorouracils may translate the short-term reduction in the risk of recurrence in patients with resected colon cancer into a delayed advantage in overall survival.