RTHP-10. IMPACT OF COMBINATION IMMUNOTHERAPY WITH TUMOR TREATING FIELDS THERAPY IN A GLIOMA COHORT

Tumor-treating fields (TTF) increase patient survival in glioblastoma, and are approved for recurrent (2011) and de novotumors (2016). Since 2012, 52 patients with gliomas at Columbia University were treated with TTF. Given preclinical data suggesting synergy between TTF and PD1-targeted therapy, the rates and outcomes of combination TTF and immunotherapy were analyzed. Of 52 patients, 40% were women. Median age at diagnosis was 58 (23-84) years. WHO glioma grade was II (6%), III (10%), or IV (84% of patients). TTF was used at recurrence in 42 (81%), with 0-4 prior recurrences. Prior therapy included bevacizumab (20%), resection (gross-total in 54%), radiation (60Gy in 85%), and temozolomide (100%). 11 (75%) patients met a compliance goal of 75%. Only 2 (4%) experienced skin toxicity requiring interruption. Concurrent systemic therapy included temozolomide (31%), nitrosourea (8%), bevacizumab (37%), or immunotherapy (54% of patients). At interim follow-up, progression free (PFS) and overall (OS) survival were 3.6 and 21.5 months, respectively. Objective response rate (ORR) based on RANO was increased in patients treated with concurrent immunotherapy (26% vs. 13%). Among GBM patients treated with concurrent immunotherapy, median PFS was significantly increased (4.6 vs. 3.5 mo, p=0.04), and survival trended upward (8.3 vs. 6.5 mo, p=0.32). After long-term follow-up, PFS, OS, and impact of compliance rates will be re-analysed. TTF improves survival for glioblastoma patients and immunotherapy shows promise in other cancers. The possible synergy between these modalities in preclinical studies and this retrospective series warrants further study in a randomized controlled trial. We propose a single-arm phase II trial of concurrent PD1 inhibitor and TTF for patients with bevacizumab-naïve glioblastoma, at diagnosis or recurrence. OS is the primary endpoint; secondary endpoints include PFS, ORR, and predictive value of PDL1 expression, and impact of compliance. Results from the EF-14 trial will serve as a historical control.