Patients with T4N0 and T1‑3N1 colon cancer and a high preoperative carcinoembryonic antigen level benefit from adjuvant chemotherapy with oxaliplatin for 6 months.

A shorter duration of oxaliplatin adjuvant chemotherapy has recently emerged as a potential option for patients with high-risk stage II and low-risk stage III (T1-3N1) colon cancer (CC). The present study aimed to elucidate the risk factors for recurrence in these patient populations and to identify the appropriate indications for shortened treatment durations. The present study retrospectively analyzed 396 patients who underwent curative surgery for pathological T4N0 or stage III CC, followed by adjuvant chemotherapy, at two institutes. Overall, 234 patients with T4N0 and low-risk stage III CC were categorized into the low-risk group and 162 patients with high-risk stage III CC into the high-risk group. The 3-year relapse-free survival rate was significantly higher in the low-risk group than in the high-risk group. Multivariate Cox model analysis of the low-risk group revealed that high preoperative serum levels of carcinoembryonic antigen (CEA) and incomplete 6-month adjuvant chemotherapy with oxaliplatin were independent poor prognostic factors. The prognosis of patients in the low-risk group who had abnormal CEA levels and did not complete the 6-month adjuvant treatment with oxaliplatin was similar to that of patients in the high-risk group. However, the prognosis of patients in the low-risk group with high CEA levels improved with a 6-month adjuvant treatment with oxaliplatin to a similar level to that of all patients with low CEA levels in the low-risk group. In conclusion, the present study suggested that the duration of adjuvant chemotherapy with oxaliplatin should not be shortened in patients with high preoperative CEA levels, even in the low-risk group.