Clinical Outcomes of Large Brain Metastases Treated With Neurosurgical Resection and Intraoperative Cesium-131 Brachytherapy: Results of a Prospective Trial

Purpose Studies on adjuvant stereotactic radiosurgery to the cavity of resected brain metastases have suggested that larger tumors (>2.0 cm) have greater rates of recurrence and radionecrosis (RN). The present study assessed the effect of permanent low-dose 131 Cs brachytherapy on local control and RN in patients treated for large brain metastases. Methods and Materials After institutional review board approval, 42 patients with 46 metastases ≥2.0 cm in preoperative diameter were accrued to a prospective trial from 2010 to 2015. Patients underwent surgical resection with intraoperative placement of stranded 131 Cs seeds as permanent volume implants in the resection cavity. The primary endpoint was local freedom from progression (FFP). Secondary endpoints included regional and distant FFP, overall survival (OS), and RN rate. Failures 5 to 20 mm from the cavity and dural-based failures were considered regional. A separate analysis was performed for metastases >3.0 cm. Results Of the 46 metastases, 18 were >3.0 cm in diameter. The median follow-up period was 11.9 months (range 0.6-51.9). The metastases had a median preoperative diameter of 3.0 cm (range 2.0-6.8). The local FFP rate was 100% for all tumor sizes. Regional recurrence developed in 3 of 46 lesions (7%), for a 1-year regional FFP rate of 89% (for tumors >3.0 cm, the FFP rate was 80%, 95% confidence interval 54%-100%). Distant recurrences were found in 19 of 46 lesions (41%), for a 1-year distant FFP rate of 52%. The median OS was 15.1 months, with a 1-year OS rate of 58%. Lesion size was not significantly associated with any endpoint on univariate or multivariate analysis. Radioresistant histologic features resulted in worse survival ( P =.036). No cases of RN developed. Conclusions Intraoperative 131 Cs brachytherapy is a promising and effective therapy for large brain metastases requiring neurosurgical intervention, which can offer improved local control and lower rates of RN compared with stereotactic radiosurgery to the resection cavity.