RTAD-01 INTRAMET: A PROSPECTIVE PHASE 2 TRIAL ON INTRAOPERATIVE RADIOTHERAPY OF BRAIN METASTASES
Frank A Giordano, Stefanie Brehmer,Abstract
Purpose
For patients with large or symptomatic brain metastases (BM), the standard treatment is surgical resection followed by adjuvant radiotherapy to the resection cavity. This prospective, single-arm, open-label phase 2 trial evaluated the safety and efficacy of low-energy X-ray intraoperative radiotherapy (IORT) in patients with resected BM.
Methods and Materials
Between 2017 and 2022, 35 patients with suspected BM were enrolled. After tumor resection and intraoperative frozen-section confirmation, IORT was delivered using a mobile low-energy X-ray device. A dose of 30 Gy was prescribed to the surface of the resection cavity. The primary endpoint was local control rate (LCR). Secondary endpoints included the incidence of distant intracranial metastases (regional control rate, RCR), overall survival (OS), time to initiation of subsequent systemic therapy, and treatment-related adverse events.
Results
The median patient age was 64 years (range, 45–85), and 54.3% of patients were male. Lung cancer was the primary tumor in 68.6% of cases. Mean tumor volume was 10.7 cm³ (SD ± 9.5). At study termination, 51.4% of patients were alive. At a mean follow-up of 25.7 months (range, 0.8–64.5 months), the LCR was 94.3% (95% CI, 82.9–98.8%), and the RCR was 57.1% (95% CI, 40.7–72.4%). Median OS was 43.6 months (95% CI, 8.8–78.4%). Leptomeningeal disease outside the irradiated field occurred in 8.6% of patients. Grade 2 or 3 radionecrosis was observed in n = 2 patients, with no identifiable associated risk factors. Overall survival did not differ significantly based on baseline Karnofsky Performance Status (p = 0.056) or development of radionecrosis (any grade, p = 0.214). The mean time to initiation of subsequent systemic therapy was 45.0 days (95% CI, 35.1–54.8). No grade 4 or 5 IORT-related adverse events were observed.
Conclusion
Intraoperative radiotherapy to the resection cavity achieved excellent local control with a safety profile comparable to postoperative stereotactic radiosurgery.