Treatment of autochthonous rat brain tumors with fractionated radiotherapy. The effects of graded radiation doses and of combined therapy with BCNU or steroids.

The avian sarcoma virus-induced glioma model in rats was used to evaluate radiation dose response (survival curves), giving fractionated treatments to the whole head. Groups of 14 to 20 rats received total doses of 2300, 4600, or 5750 rads over 2, 4, or 5 weeks, respectively. Median group survival times were compared to controls and to each other. All doses of radiation significantly prolonged survival with reference to control. The 4600- and 5750-rad doses were significantly more effective than the 2300-rad dose. In another series of experiments, BCNU chemotherapy (10 mg/kg) was combined with 2300 and 4600 rads radiation therapy. Synergism of therapies was demonstrated. Methylprednisolone acetate (2 mg/kg twice weekly over 4 weeks) alone did not affect survival curves, and its combination with 4600 rads radiation therapy negated the prolongation of survival achieved with 4600 rads alone.