POSTOPERATIVE RADIOTHERAPY FOR LOCALLY ADVANCED COLON-CANCER

Background: The role of adjuvant postoperative radiotherapy for locall y advanced colon cancer is not well documented. Methods: Seventy-eight patients who underwent a complete resection of B2-C colon cancer rece ived postoperative radiotherapy. Twenty-eight patients received less t han or equal to 45 Gy; 50 patients received 50-55 Gy. Twenty-seven pat ients received adjuvant fluorouracil-based chemotherapy, All patients were followed for a minimum of 3 years; no patients were lost to follo w-up. Results: The overall local control rate was 88%. The 5-year actu arial rate of local control was 96% after 50-55 Gy postoperative radio therapy compared with 76% after <50 Gy (p = 0.0095). Multivariate anal ysis of local control showed that only radiotherapy dose significantly influenced this end point. Cause-specific survival rates at 5 years w ere B2, 67%; B3, 90%; C1, 100%; C2, 61%; C3, 36%; and overall, 63%. Mu ltivariate analysis of cause-specific survival showed that only stage significantly influenced this end point. Bowel obstruction caused by a dhesions developed in three patients and required a laparotomy; radiat ion-induced sarcoma developed in one additional patient. Conclusions: Postoperative radiotherapy appears to reduce the risk of local recurre nce in patients with locally advanced colon cancer. The optimal dose i s probably 50-55 Gy at 1.8 Gy per fraction. Postoperative radiotherapy may improve cause-specific survival for patients with stages B3 and C 2 cancers.