Response of the 9L rat brain tumor to combination treatment with radiation and bleomycin

The therapeutic efficacy of combined modality treatment with radiation therapy and bleomycin was investigated in rats burdened with the intracerebral 9L gliosarcoma. Both radiation (single or fractionated exposures) and bleomycin (injected intracerebrally directly into the tumor region) are effective in prolonging survival when used as single agents. Bleomcyin (1.0 mg/kg/week) combined with low-dose radiation therapy (15.3 Gy in 6 fractions in 2 weeks) prolonged survival over that of radiation alone, but not to the extent of high-dose radiation therapy (30.6 Gy in the same schedule). Bleomycin was effective whether given simultaneously or following fractionated radiation therapy-the important factor being delivery of radiation therapy early in the disease process. The greatest enhancement in survival caused by combination therapy compared to that by single agent therapy was observed when single exposure radiation therapy (20 Gy) followed single bleomycin administration by 4 hr. These results suggest the possibility of using bleomycin as an adjunct to radiation therapy for the treatment of patients with malignant brain tumors.