MR OF TOXIC EFFECTS OF ACCELERATED FRACTIONATION RADIATION-THERAPY AND CARBOPLATIN CHEMOTHERAPY FOR MALIGNANT GLIOMAS

PURPOSE: To present MR findings of parenchymal brain injury after acce lerated fractionation radiation therapy combined with carboplatin chem otherapy in the treatment of malignant brain gliomas. METHODS: Eighty- one evaluable subjects in an ongoing treatment protocol for malignant gliomas form the patient base for this report. After surgical resectio n of tumors, patients underwent a course of accelerated fractionation radiation therapy to a total dose of 60 Gy, Carboplatin was infused in travenously before each radiation treatment. Precontrast and postcontr ast MR scans were obtained before treatment and at 4-week intervals af terward and were analyzed retrospectively. RESULTS: Posttreatment MR i maging in 20 of the 81 patients showed development of unusual parenchy mal lesions or enlarging masses needing debulking, and these patients underwent second operations. Two groups emerged: those with tumor and necrotic brain (n = 11) and those with necrosis and reactive gliosis b ut no definitive tumor (n = 9). Enhancing lesions in the tumor-negativ e group appeared later than those in the tumor-positive group, were of ten multiple, and were usually located several centimeters away from t he tumor resection site or even contralaterally, Common locations were the corpus callosum and corticomedullary junctions. Lesions in the tu mor-positive group were more often solitary and located immediately ad jacent to the surgical site. Positive and negative results of positron emission tomography with fludeoxyglucose F 18 were obtained in both g roups. The incidence of brain necrosis without associated tumor was 11 %. CONCLUSIONS: A pattern of unusual enhancing parenchymal brain lesio ns was seen on MR imaging after accelerated fractionation radiation th erapy and concomitant carboplatin chemotherapy. The abnormalities seem more extensive than focal necrotic lesions on enhanced CT or MR imagi ng after conventional radiation therapy, and they may mimic recurrent tumor.