Reirradiation with Proton Therapy for Recurrent Gliomas

Abstract

Purpose: To evaluate the effectiveness and tolerance of reirradiation with proton therapy (PT) in patients with recurrent gliomas. Patients and Methods: Between 2005 and 2012, 20 patients with recurrent gliomas were irradiated with proton therapy at the Indiana University Health Proton Therapy Center. Three had low-grade gliomas (LGGs, World Health Organization grade I/II), 4 had grade III, and 13 had glioblastoma (GBM, World Health Organization grade IV). The median time interval between initial radiation and reirradiation was 17.4, 62.8, and 15.3 months for LGG, grade III gliomas, and GBMs, respectively. The median dose delivered was 30, 59.4, and 54 Gy (RBE) for the low-grade, grade III, and grade IV tumors, respectively. Results: The median follow-up time from reirradiation was 8.3 months (range, 1.4 to 25.3), and 30% of the patients were alive at time of follow-up evaluation. Only 1 patient with an LGG had died. Median overall survival (OS) from the time of the original pathologic diagnosis was 115.9 months and 20.4 months, respectively, for grade III gliomas and GBMs. Median survival from completion of reirradiation was 24.9 months for grade III gliomas and 7.8 months for GBMs. On univariate analysis, significant factors associated with OS from the original pathologic diagnosis included age at retreatment, interval between prior radiation and proton therapy, and extent of surgical resection. Grade and prior radiotherapy dose were borderline significant. Age was the only significant factor associated with OS from retreatment. Most patients tolerated reirradiation well; however, 2 patients experienced radiation necrosis. One was treated surgically and the other with steroids and hyperbaric oxygen therapy. Conclusion: Proton reirradiation of recurrent gliomas was generally well tolerated and associated with favorable long-term survival in patients with LGGs and grade III gliomas. The 10% rate of radiation necrosis was modest given the high cumulative dose is these patients.