Radiation myelitis following craniospinal irradiation with concurrent actinomycin-D therapy

Two patients are presented who developed radiation myelitis as a complication of treatment for medulloblastoma. These patients had been entered onto a pilot study to evaluate the therapeutic efficacy of combined treatment with radiation therapy and actinomycin-D (AMD). AMD is a known radiation enhancer in all tissues but the nervous system. Both of these patients received a full course of cranio-spinal irradiation plus AMD 15 mcg/kg for the first five days of therapy. One patient developed myelitis at 4 months, and the other at 12 months after treatment. Both patients are surviving three years posttreatment without any evidence of recurrent disease. The myelitis in one patient has improved, and it is stable in the other patient. It is concluded that AMD enhances the effect of radiation therapy on the central nervous system. This has never been reported but is important to note now, since radiation enhancers are included in multimodal treatment regimens for a variety of malifnant conditions. Reduction of radiation dose may be necessary when large volumes of the nervous system are treated.