Predictors of interstitial brachytherapy utilization in locally advanced cervical cancer and impact on overall survival.

Purpose: For locally advanced cervical cancer (LACC), the addition of brachytherapy (BT) improves overall survival (OS), and interstitial BT has been prospectively shown to improve target and organ at risk dose. Brachytherapy is less common in patients without insurance, underrepresented minorities, and in low-volume cancer centers, which may in turn widen cancer disparities. In this study, we utilized the National Cancer Database (NCDB) to examine the patterns and predictors of interstitial brachytherapy in patients with LACC, and its impact on OS. Material and methods: Patients with LACC (stage IIB-IVA) diagnosed between 2004-2018 and treated with radiation were included. A logistic regression model was fit with the predictors, such as race, nodes, T-stage, facility type, age, and Charlson-Deyo score, to estimate the probability of receiving interstitial brachytherapy treatment and to calculate propensity scores. Cox regression model was defined using the calculated propensity scores as a covariate to examine the effect of brachytherapy group on OS. Results: In the study, 9,829 patients were included, and 15% of them received interstitial BT. On multivariable analysis, a higher stage and treatment at an academic center were associated with increased interstitial BT. African American patients and those with positive nodes were less likely to receive interstitial BT. After propensity score matching, there was no OS difference between patient treated with interstitial vs. intracavitary BT (HR: 0.985, Conclusions: Our work supports the growing body of literature on BT utilization impacted by patient race and treatment facility. Patients with a higher stage of cervical cancer and those treated at a high volume or academic center were more likely to receive interstitial BT, reflecting appropriate intensification of therapy for larger tumors. Interstitial BT did not indicate an OS benefit. Further study could lead to improved understanding of barriers to accessing interstitial brachytherapy.