ADENOCARCINOMA OF THE RECTUM TREATED BY RADICAL EXTERNAL RADIATION-THERAPY

Purpose: To assess the long-term survival and response rates of patien ts with primary rectal cancer to radical radiation therapy. Methods an d Materials: Between 1978 and 1987, 229 patients were treated at the P rincess Margaret Hospital with radical external radiation therapy for adenocarcinoma of the rectum. Patients were treated with radiation eit her because they were considered to have unresectable tumors, were med ically unfit, or refused surgery, or for a combination of these factor s. Doses ranged from 40 Gy in 10 fractions by a split course over 6 we eks to 60 Gy in 30 fractions in 6 weeks. The most commonly prescribed treatment was 52 Gy target absorbed dose in 20 daily fractions over 4 weeks. Results: The overall 5-year actuarial survival rate was 27%; fo r patients with mobile tumors, it was 48%, partially fixed 27%, and fi xed tumor 4%. Forty-eight of the 97 patients (50%) with mobile tumors, 11 of the 37 patients (30%) with partially fixed tumors, and 7 of the 77 patients (9%) with fixed tumors had clinically complete tumor regr ession following radiation. Of these, 18 of the mobile, 6 of the parti ally fixed, and 5 of the fixed tumors later relapsed locally. Fifty pa tients had salvage surgery after failing to achieve complete remission or for local relapse, with a 5-year actuarial survival rate of 42% fr om the time of surgery. Conclusion: Although radiation therapy can cur e some patients with mobile or partially fixed rectal adenocarcinomas who refuse or are unsuitable for surgery, local control remains a prob lem; salvage surgery should be considered in patients who relapse or f ail to go into complete remission and who are fit to undergo surgery. For patients with fixed rectal cancers, high-dose external-beam radiat ion should be part of a planned preoperative regimen or be palliative in intent.