Reirradiation for recurrent malignant brain tumor with radiotherapy or proton beam therapy Technical considerations based on experience at a single institution

Radiotherapy for recurrent malignant brain tumors is usually limited because of the dose tolerance of the normal brain tissue. The goal of the study was to evaluate the efficacy and feasibility of reirradiation for patients with recurrent malignant brain tumors. The subjects comprised 26 patients with recurrent malignant brain tumors treated with conventional radiotherapy (RT, n = 8), stereotactic radiotherapy (SRT, n = 10), and proton beam therapy (PBT, n = 8) at our institute. Fifteen patients had glioblastoma, 6 had WHO grade 3 glioma, and 5 had other tumors. The dose of initial radiotherapy was 34.5-94.4 Gy. Different radiation schedules were compared using the equivalent dose in 2-Gy fractions. Reirradiation was completed in all patients without a severe acute reaction. The reirradiation doses were 30-60 Gy (median, 42.3 Gy) and the total doses for the initial and second treatments were 64.5-150.4 Gy (median, 100.0 Gy). Currently, 11 patients are alive (median follow-up period, 19.4 months) and 15 are dead. The median survival and local control periods after reirradiation of the 26 patients were 18.3 and 9.3 months, respectively. For the 15 patients with glioblastoma, these periods were 13.1 and 11.0 months, respectively. Two patients showed radiation necrosis that was treated by surgery or conservative therapy. Reirradiation for recurrent malignant brain tumor using conventional RT, SRT, or PBT was feasible and effective in selected cases. Further investigation is needed for treatment optimization for a given patient and tumor condition.