Initial Clinical Outcomes in the Treatment of Brain Metastasis with Gyroscopic Radiosurgery at a Single Institution.

INTRODUCTION:Brain metastases occur in approximately 20% to 40% of individuals annually diagnosed with cancer. This poor prognostic feature can severely reduce life expectancy and quality of life. Stereotactic radiosurgery (SRS) has been shown to provide excellent tumor control and clinical outcomes. ZAP-X (Zap Surgical Systems Inc., San Carlos, CA, USA) is an innovative self-shielded gyroscopic stereotactic radiosurgery (GRS) system to help further address these needs. In this study, we evaluate the clinical outcomes of patients with brain metastases who have undergone treatment with ZAP-X in a single institution. METHODS:Medical records of all patients with brain metastases treated with GRS between May 2021 and May 2023 were reviewed as a retrospective case series. Demographics, clinical symptoms, treatment trajectory, and follow-up data were collected and analyzed. RESULTS:A total of 46 patients with 140 combined brain metastases were included in this cohort. Of them, 58.7% (N=27) were female patients, and the mean age was 63 years (range 36-82). The primary pathologies were non-small cell lung cancer (NSCLC; N22, 47.8%), breast cancer (N11, 23.9%), melanoma (N5, 10.9%), and others (N8, 17.4%). The prescription dose was 18 Gy if the patient previously received whole-brain radiotherapy (WBRT); otherwise, 20 Gy. All patients received dexamethasone (3x4 mg PO). The most common symptoms included headache (45.7%), motor disturbances (30.4%), and seizures (21.7%). Mean follow-up time was 8.5 months (range 0-19). Systemic response using Response Evaluation Criteria in Solid Tumors (RECIST) criteria was 17.3% complete response, 10.9% partial response, 45.7% stable disease, and 26.1% progression of disease. Tumor control was 73.9% according to the Response Assessment in Neuro-Oncology (RANO) criteria for brain metastases. CONCLUSIONS:GRS is a novel image-guided linear accelerator-based, self-shielding gyroscopic radiosurgery platform that does not require a vault. This study shows that GRS achieves comparable results to traditional SRS platforms in the treatment of brain metastases.