Frameless Linac-based Radiosurgery for Benign Intracranial Tumors Treated with HyperArc: Analysis of Tumor Control and Toxicity

Purpose: HyperArc™ (HA) automates both planning and delivery of single-isocenter VMAT radiosurgery (SRS) and was designed for complex multi-metastasis cases. The clinical effectiveness of treating benign intracranial tumors (BIT) with HA is unknown. We collected data on treatment planning, delivery, and clinical outcomes of BIT managed with SRS since HA deployment. Methods: Patients received SRS using HA from 2017-2021 at a single institution. Prescription dose was normalized to ≥ 99% of gross tumor volume. Treatments were delivered on Varian Edge linear accelerator with 10MV flattening-filter free beam at up to 2400 MU/min with high-definition multi-leaf collimator. Post-treatment imaging, toxicities, and outcomes were assessed. Results: 198 BIT targets (min=0.1cc, max=58.9cc) were treated. Common pathologies were meningiomas (130), pituitary adenomas (30), and acoustic schwannomas (23). Nearly half (45.1%) were treated in a single fraction (12-22Gy) versus 54.9% with fractionated SRS (24-35Gy). Mean RTOG CI and Paddick GI were 1.12 and 3.31, respectively. A majority (74%) were treated with 3 arcs with mean total treatment lasting 10.5 minutes. Mean FU was 2.6 years. 20 of 198 (10.1%) tumors progressed with mean time to failure being 2.1 years. Tumor progression occurred in 10.1%, mostly in recurent WHO II meningiomas. Of those that progressed, 19 were meningiomas with 17 being WHO grade 2 with prior surgery. Grade 3+ CNS toxicity was reported in 4.3% of patients, with 98.9 and 99.5% hearing and visual preservation, respectively. Conclusions: HA efficiently delivers high-quality plans with sharp dose fall-off for BIT, with early clinical outcomes and toxicity consistent with historical controls.