Multicenter, Phase 1, Dose Escalation Study of Hypofractionated Stereotactic Radiation Therapy With Bevacizumab for Recurrent Glioblastoma and Anaplastic Astrocytoma

Purpose: To establish the maximum tolerated dose of a 3-fraction hypofractionated stereotactic reirradiation schedule when delivered with concomitant bevacizumab to treat recurrent high-grade gliomas. Methods and Materials: Patients with recurrent high-grade glioma with Karnofsky performance status ≥60, history of standard fractionated initial radiation, tumor volume at recurrence ≤40 cm³, and absence of brainstem or corpus callosum involvement were eligible. A standard 3+3 phase 1 dose escalation trial design was utilized, with dose-limiting toxicities defined as any grade 3 to 5 toxicities possibly, probably, or definitely related to radiation. Bevacizumab was given at a dose of 10 mg/kg every 2 weeks. Hypofractionated stereotactic reirradiation was initiated after 2 bevacizumab doses, delivered in 3 fractions every other day, starting at 9 Gy per fraction. Results: A total of 3 patients were enrolled at the 9 Gy × 3 dose level cohort, 5 in the 10 Gy × 3 cohort, and 7 in the 11 Gy × 3 cohort. One dose-limiting toxicity of grade 3 fatigue and cognitive deterioration possibly related to hypofractionated stereotactic reirradiation was observed in the 11 Gy × 3 cohort, and this dose was declared the maximum tolerated dose in combination with bevacizumab. Although no symptomatic radionecrosis was observed, substantial treatment-related effects and necrosis were observed in resected specimens. The intent-to-treat median overall survival was 13 months. Conclusions: Reirradiation using a 3-fraction schedule with bevacizumab support is feasible and reasonably well tolerated. Dose-escalation was possible up to 11 Gy × 3, which achieves a near doubling in the delivered biological equivalent dose to normal brain, in comparison with our previous 6 Gy × 5 schedule. Promising overall survival warrants further investigation.