Application of 200 kHz Tumor Treating Fields (TTFields) in Patients With Infratentorial High-Grade Glioma: Case Series.

Tumor treating fields (TTFields) therapy at 200 kHz is FDA-approved for supratentorial glioblastoma. However, reports of TTFields in patients with infratentorial high-grade glioma (HGG) are rare. Two patients with infratentorial HGG received off-label 200 kHz TTFields. To reduce impaired neck range of motion, the electrode transducer arrays were "skeletonized" by cutting a portion of the adhesive material. The electrode arrays were applied with the neck in flexion to further promote range of neck motion. Patient 1, a 22-year-old man with high-grade diffuse pontine glioma with recurrences and prior treatments, tolerated TTFields combined with systemic treatment (initially with a bifunctional DNA alkylating agent; subsequently with temozolomide and bevacizumab) for 5 months with stable disease for 4 months. He experienced grade 1 rash (neck). Patient 2, a 58-year-old woman with diffuse glioma of the brainstem (H3K27M-mutated) with multiple recurrences and prior treatments, tolerated TTFields combined with systemic treatment (lomustine and bevacizumab). With the TTFields + systemic combination therapy, the patient was stable for 8 months with no TTFields-related side effects. We provide two initial post-marketing cases demonstrating 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.