Postoperative radiation therapy of rectal cancer.

Beginning in December 1975, at the Massachusetts General Hospital (MGH) patients with rectal carcinomas thought to be at high risk of local recurrence after potentially curative surgical resection, were entered on a treatment protocol of high dose postoperative radiation therapy. Treatment was given with X rays of 10 MeV, generally using a four-field box technique to a dose of 4500 cGy with a boost to 5040 cGy or higher when the small bowel could be excluded from the reduced field. One-hundred sixty-five patients who began their radiation therapy between December 1975 and December 1982 were entered into the study. The median age was 65 years. The median follow-up in the survivors was 56 months, with a minimum follow-up of 17 months. All but 10 patients were followed for more than 2 years. Of the entire group, the actuarial 5-year survival was 53%, with survival of 71% in patients with Stage B-2, 39% in Stage C-2, and 17% in Stage C-3. Local failure was seen in 5/53 patients with Stage B-2 disease and 0/7 of patients with Stage B-3 disease. In patients with positive lymph nodes, local failure occurred in 2/10 (20%) of patients with Stage C-1, 16/77 (21%) of Stage C-2, and 8/15 (53%) of patients with Stage C-3 disease. Compared to previous series of surgery alone, the local failure rate has been decreased by more than one-half in all patients, except those with Stage C-3. Efforts to maximize the radiation doses in all stages should be made to minimize local failure. For Stage C-3, newer strategies such as intraoperative radiation therapy should be employed to decrease the continuing high incidence of failures.