CTIM-18. PHASE 2 STUDY OF PD-1 BLOCKADE WITH PEMBROLIZUMAB PLUS RE-IRRADIATION FOR RECURRENT GLIOBLASTOMA (RGBM) (NCT03661723)

Abstract Re-irradiation is therapeutically considered for select rGBM patients and may induce immunogenic cell death to stimulate anti-tumor immune responses. Our phase 2 study of re-irradiation with pembrolizumab among evaluated the efficacy safety this regimen. METHODS Adult KPS ≥ 70, a maximum supratentorial tumor diameter 6 cm who were on ≤ 2mg dexamethasone/day months from initial conventional radiation therapy eligible. Cohort A (bevacizumab [BEV]-naïve) had prior progressions while cohort B (BEV-refractory) allowed unlimited but only one BEV. included 35 Gy over 10 fractions residual enhancing (cohort A) as well + non-enhancing B) disease. Pembrolizumab was administered at 200 mg every three weeks beginning within week start. BEV 15 mg/kg only. RESULTS Sixty enrolled (n = 30 per cohort) median age 61 years (range 20-76), 47% female 53% after or more progressions. Grade 3 events deemed least possibly related in > patient headache 2) elevated ALT hypertension 5). No grade 4 occurred than single no 5 occurred. Median PFS PFS-6 4.9 (95% CI: 3.5, 5.6) 26.0% 12.3%, 43.0%) 4.14 3.45, 5.42) 16.9% 5.4, 33.7) B. survival cohorts 11.5 9.6, 14.1) 7.6 CI 5.5, 9.3), respectively. CONCLUSIONS overall tolerated achieved comparable historical salvage established lomustine.