Radiation therapy and 100 per cent oxygen breathing in the treatment of adenocarcinomas of the large bowel. A controlled study.

The oxygen effect is a well established radiobiologic principle. The exploitation of this effect in clinical radiation therapy has not been particularly rewarding. The work of Cater and Silver (1) and Rubin (2) has indicated, however, that breathing 100 per cent oxygen at atmospheric pressure during conventionally fractionated radiation therapy is worthy of investigation. In 1964, our group undertook a study of patients with adenocarcinoma of the large bowel in whom the lesion was unresectable at the time of operation, or biopsy verified a recurrent tumor. There was no clinical or laboratory evidence of distant metastasis. All known tumor could be encompassed within radiation-therapy portals of 20 × 20 cm or less. All patients were treated with supravoltage radiation therapy at the rate of 1,000 to 1,200 rads in five to six fractions per week to a total midplane dose of 3,750 to 4,500 rads. Composition of the treatment groups was determined by random selection. Onehalf the patients breathed 100 per cent o...