Receipt of brachytherapy is an independent predictor of survival in glioblastoma in the Surveillance, Epidemiology, and End Results database.

Abstract

There has been a resurgence of interest in brachytherapy as a treatment for glioblastoma, with several currently ongoing clinical trials. To provide a foundation for the analysis of these trials, we analyze the Surveillance, Epidemiology, and End Results (SEER) database to determine whether receipt of brachytherapy conveys a survival benefit independent of traditional prognostic factors. We identified 60,456 glioblastoma patients, of whom 362 underwent brachytherapy. We grouped patients based on receipt of brachytherapy and compared clinical and demographic variables between groups using Student's t-test and Pearson's chi-squared test. We assessed survival using Kaplan-Meier curves and Cox proportional hazards models. Median overall survival was 16months in patients who received brachytherapy compared to 9months in those who did not (log-rank p < 0.001). Patients who underwent brachytherapy tended to be younger (p < 0.001), suffered from smaller tumors (<4cm, p < 0.001), and were more likely to have undergone gross total resection (GTR, p < 0.001). In univariable Cox models, these variables were independently associated with improved overall survival. Additionally, improved survival was associated with known receipt of chemotherapy (HR 0.459, p < 0.001), external beam radiation (HR 0.447, p < 0.001), and brachytherapy (HR 0.637, p < 0.001). The association between brachytherapy and improved survival remained robust (HR 0.859, p = 0.031) in a multivariable model that adjusted for patient age, tumor size, tumor location, GTR, receipt of chemotherapy, and receipt of external beam radiation. Our SEER analysis indicates that brachytherapy is associated with improved survival in glioblastoma after controlling for age, tumor size/location, extent of resection, chemotherapy, and external beam radiation.