Re-Irradiation and Its Contribution to Good Prognosis in Recurrent Glioblastoma Patients.

BACKGROUND: Radiation therapy, one of the strongest anti-cancer treatments, is already performed to treat primary glioblastoma; however, the effect of repeated radiation therapy for recurrent tumors has not been fully explored. The aim of this study was to determine the efficacy of re-irradiation in treating recurrent glioblastoma. METHODS: The study included 36 patients with recurrent glioblastoma treated with repeated radiation therapy between 2002 and 2016. Stereotactic radiosurgery (SRS) and hypo-fractionated stereotactic radiotherapy (HSRT) were performed in these patients. RESULTS: Fourteen patients received SRS with a median dose of 25 Gy (range, 20-32 Gy) in 1-5 fractions. Twenty-two patients received HSRT with a median dose of 40 Gy (range, 31.5-52 Gy) in 6-20 fractions. There were six treatment-related grade 3 adverse events. Survival analysis showed that re-irradiation significantly prolonged overall survival (OS) and progression-free survival (PFS). The median OS and one-year OS rate after re-irradiation were 17.2 months and 60.4%, respectively. The median PFS and 6-month PFS rate after re-irradiation were 4.4 months and 41.9%, respectively. Of the 36 patients, three survived without any progression in their condition. CONCLUSION: Re-irradiation for recurrent glioblastoma showed favorable outcomes. Radiation dose and fractionation should be carefully considered to minimize radiation necrosis.