The effect of prednisone and irradiation on the rectum in dogs.

In an attempt to diminish the severity of the acute and late effects of irradiation to the rectum of dogs, oral prednisone was administered to 10 dogs for 1 week prior to, during, and for 1 month following a 3-week fractionated course of 60Co exposures to the pelvis. A control group of 10 dogs received irradiation alone. The dogs were observed clinically, serial rectal biopsies were done during and following the acute reaction, and the rectum was studied following sacrifice. Observations suggest that prednisone has no beneficial effect on the acute inflammatory reaction, and increases the severity of the late tissue damage.