INNV-34. APPLICATION OF 200 KHZ TUMOR TREATING FIELDS (TTFIELDS) IN PATIENTS WITH INFRATENTORIAL HIGH-GRADE GLIOMA: CASE SERIES

Abstract BACKGROUND 200 kHz Tumor Treating Fields (TTFields) therapy is FDA-approved for supratentorial newly-diagnosed and recurrent glioblastoma. However, reports of its application in patients with infratentorial high-grade glioma (HGG) are rare. Based on computational modeling, the therapeutic field strength (~1 V/cm peak-to-peak) is thought to be achievable for infratentorial HGG. METHODS Two patients with infratentorial HGG received off-label 200 kHz TTFields therapy with the Optune® device (Novocure, Ltd.). To reduce impaired range of motion of the neck, the electrode transducer arrays were “skeletonized” by cutting a portion of the adhesive material surrounding them. Application of the electrode arrays was performed with the neck in flexion, to further promote neck range of motion. Cloth tape was used for reinforcement as necessary. Electrode arrays were changed every 2-3 days. We report the results of patient survival and adverse events. RESULTS Patient 1: 22-year-old man with high-grade diffuse pontine glioma with recurrences and prior treatments (including radiation, temozolomide, lomustine, and dopamine receptor D2 [DRD2] antagonist), tolerated TTFields combined with systemic treatment (initially with a bi-functional DNA alkylating agent; subsequently with temozolomide and bevacizumab) for 5 months with stable disease for 4 months. He experienced grade 1 rash of the neck. Patient 2: 58-year-old woman with diffuse glioma of the brainstem (H3K27M-mutated) with multiple recurrences and prior treatments (including concurrent radiation and temozolomide, and DRD2 antagonist), tolerated TTFields combined with systemic treatment (lomustine and bevacizumab). The TTFields infratentorial layout was iteratively modified with respect to placement of the electrode transducer arrays, for improved tolerability. With the TTFields+systemic combination therapy, the patient was stable for 8 months with no local TTFields-related side effects. CONCLUSIONS We provide initial post-marketing evidence that off-label use of 200 kHz TTFields in infratentorial HGG is safe and feasible. Prospective studies are necessary to validate the efficacy of this approach.