Intraoperative, Interstitial Brachytherapy in Newly Diagnosed Brain Metastases Through Cesium-131 Collagen Tile Implant: A Multi-Institutional Case Series

Background Cesium-131 collagen tile has gained traction as an intraoperative brachytherapy platform for recurrent intracranial tumors, but outcome data in newly diagnosed brain metastases (nBM) remain sparse, with fewer than ten cases reported. This study evaluates the safety and efficacy of cesium-131 collagen tiles in nBM patients. Methods Clinical information was collected for consecutive nBM patients treated at three neurosurgical centers. Local control and overall survival (OS) were calculated. Results The cohort comprised 36 patients (14 men, 22 women; mean age, 62.1 ± 8.9 years) with 39 nBM. Histologies included lung (n = 19), melanoma (n = 8), breast (n = 4), gastrointestinal (n = 3), and genitourinary (n = 5) metastases. The mean pre-operative tumor diameter was 3.29 cm ± 1.35 cm. Gross total resection was achieved in all but one case. Mean Karnofsky Performance Score (KPS) before resection/tile implant was 81 ± 11.1. The average hospital stay was 2.2 ± 1.6 days. Thirty-day and ninety-day readmission rates were 25.0% and 19.4%, respectively; there were no unplanned returns to the operating room. With a median follow-up of 328 days, one-year actuarial local control was 100%, with one recurrence at two years. Median OS was 182 days. Radiation necrosis was observed in one patient (2.6%). KPS improved or remained stable in 28 patients and declined in 8 (22.2%). A decline in KPS at one month post-procedure was associated with shorter OS (65 vs. 211 days; P = .02). Conclusion This multi-institutional study provides the first dedicated evaluation of cesium-131 collagen tiles for the treatment of nBM, demonstrating excellent safety and local control.