Outcomes of surgical resection combined with intraoperative cesium-131 brachytherapy in brain metastases: A systematic review and meta-analysis.

e14014 Background: Local control after surgical resection of brain metastases remains difficult to achieve. Although postoperative stereotactic radiosurgery (SRS) and whole-brain radiotherapy (WBRT) improve intracranial control, both approaches can delay treatment and increase the risk of radiation necrosis and cognitive decline, particularly in patients with large or rapidly growing tumors. Intraoperative cesium-131 (Cs-131) brachytherapy allows immediate, targeted radiation to the resection cavity and may help address these challenges. However, available evidence is limited, and outcomes have not been well quantified. Methods: We performed a systematic review and single-arm meta-analysis following PRISMA guidelines to evaluate outcomes after surgical resection with intraoperative Cs-131 brachytherapy in patients with recurrent or high-risk newly diagnosed brain metastases. Event rates and standard errors were extracted and pooled using a random-effects model. Heterogeneity was assessed using the I² statistic, and sensitivity analyses were conducted by excluding outlier studies. Primary outcomes included local freedom from progression (LFFP), radiation necrosis, and surgical complications. Results: Nine studies including 479 patients were analyzed. The pooled LFFP rate was 0.61 (95% CI, 0.29–0.94; p = 0.0002), with considerable heterogeneity (I² = 100%). After excluding three outlier studies, LFFP increased to 0.93 (95% CI, 0.91–0.96; p < 0.00001), with no remaining heterogeneity. Radiation necrosis was reported in five studies (n = 296) and occurred in 11% of patients (95% CI, 0.05–0.18; p = 0.001), decreasing to 9% (95% CI, 0.03–0.14; p = 0.01) on sensitivity analysis. Surgical complications were observed in 11% of patients (4 studies; 95% CI, 0.08–0.13; p < 0.00001; I² = 23%). Conclusions: Surgical resection with intraoperative Cs-131 brachytherapy is associated with high rates of local control and a low incidence of treatment-related toxicity in patients with brain metastases. When adjusted for outliers, local control rates approach 93%, comparing favorably with published outcomes for postoperative SRS. Importantly, immediate radiation delivery may reduce treatment delays without increasing surgical risk. While these findings are encouraging, they are based on small, heterogeneous retrospective studies. Prospective trials are needed to better define the role of Cs-131 brachytherapy alongside standard postoperative radiation approaches.