Radiation therapy in the conservative management of cancers of the low rectum and anal canal.

Radiotherapy has gained a prominent place in the management of cancer of the rectum and anus. In 221 cases of epidermoid carcinoma of the anal canal not involving more than three quarters of the circumference of the anal canal or the vaginal mucosa combined external beam using 60 Cobalt (30 Gy over 19 days) with an iridium implant boost (10-20 Gy) 2 months later resulted in a 5-year survival rate of 65%. Ninety percent of patients had normal anal function. A series of 281 patients with "early" adenocarcinoma of the rectum was treated by intracavitary irradiation (50 Kv energy, 100-150 Gy in 3-4 applications over 6 weeks). They were selected as being confined to the bowel wall without evidence of lymphadenopathy or anaplasia. Five-year survival and local recurrence rates were 78% and 5% respectively. A further series of 64 patients with more extensive "intermediate" type adenocarcinoma of the lower third of the rectum selected on the basis of age and poor surgical risk were treated by external beam 60 Cobalt irradiation (30 Gy over 12 days) followed by intracavitary and 192 iridium inplant after a two month interval. Of 44 patients treated more than 3 years previously the local control rate was 79.5% and survival 83%. These results suggest that radiotherapy might be applied to more extensive rectal carcinomas which otherwise would require total rectal excision.