Postoperative radiotherapy for locally advanced colon cancer

Background: The role of adjuvant postoperative radiotherapy for locally advanced colon cancer is not well documented. Methods: Seventy-eight patients who underwent a complete resection of B2-C colon cancer received postoperative radiotherapy. Twenty-eight patients received ⩽45 Gy; 50 patients received 50–55 Gy. Twenty-seven patients received adjuvant fluorouracil-based chemotherapy. All patients were followed for a minimum of 3 years; no patients were lost to follow-up. Results: The overall local control rate was 88%. The 5-year actuarial rate of local control was 96% after 50–55 Gy postoperative radiotherapy compared with 76% after <50 Gy (p=0.0095). Multivariate analysis of local control showed that only radiotherapy dose significantly influenced this end point. Cause-specific survival rates at 5 years were B2, 67%; B3, 90%; C1, 100%; C2, 61%; C3, 36%; and overall, 63%. Multivariate analysis of cause-specific survival showed that only stage significantly influenced this end point. Bowel obstruction caused by adhesions developed in three patients and required a laparotomy; radiation-induced sarcoma developed in one additional patient. Conclusions: Postoperative radiotherapy appears to reduce the risk of local recurrence in patients with locally advanced colon cancer. The optimal dose is probably 50–55 Gy at 1.8 Gy per fraction. Postoperative radiotherapy may improve cause-specific survival for patients with stages B3 and C2 cancers.