Unexpected toxicity from radiation therapy in two patients with Kaposi's sarcoma receiving interferon

Two homosexual men with Kaposi's sarcoma and acquired immune deficiency received radiation therapy to the oral mucosa while treatment with recombinant leukocyte A interferon was being given systemically at a dose of 36 million units. Symptoms of radiation mucositis developed after the administration of 900 rad in the first patient and 1,050 rad in the second patient. Radiation therapy had to be stopped after doses of 1,100 and 2,100 rad, respectively, had been given. Both patients had to be admitted to the hospital for supportive care and the second patient required placement of a feeding tube. To our knowledge, no other clinical observations suggesting interactions of radiation therapy and interferon have been reported. We discuss the results of experiments with cultured cells and experimental animals which suggest that such interactions occur and may be successfully exploited therapeutically.