Node Positive Prostate Cancer Treated with Brachytherapy Boost

• Published in: International journal of radiation oncology, biology, physics Vol. 120; no. 2; p. e513
• Main Authors: Barve, R., Youssef, I., Kollmeier, M.A., Brennan, V.S., Shasha, D., Pandya, S., Gorovets, D.
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 01.10.2024
• ISSN: 0360-3016
• DOI: 10.1016/j.ijrobp.2024.07.1139

High risk prostate cancer patients with node positive (cN1) disease are treated with radiation therapy along with androgen deprivation therapy (ADT): however, it is unknown if this population might benefit from brachytherapy (BT) boost. In this study we evaluated survival outcomes in cN1 patients treated with definitive radiation therapy that included a BT boost. We retrospectively identified cN1 prostate cancer patients treated at our institution between 2008 to 2020 with brachytherapy boost, external beam radiation therapy (EBRT) and androgen deprivation therapy (ADT). Time to event analysis for progression free survival (PFS) and overall survival (OS) were estimated using the Kaplan-Meier method. Univariate and Multivariable Cox regression model were used to estimate the hazard ratio (HR) associated with the covariates. We identified 38 cN1 patients. The median age was 66 years (range = 50-79 years) at the time of diagnosis. All patients underwent BT boost with low dose rate (37%) with Pb-103/I-125 (100-110 Gy) or high dose rate (63%) with Ir-192 (15 Gy) followed by pelvic EBRT to 45 Gy with an involved nodal boost to 56.25 Gy. All patients received ADT with leuprolide alone or in combination of bicalutamide or abiraterone/prednisone. Median duration of ADT was 15 months. Median follow-up was 49 months, PFS at 3, 5, and 10 years was 81%, 65%, and 28% respectively. OS at 3, 5 and 10 years was 100%, 94%, and 71% respectively. Duration of ADT was significantly associated with PFS on univariate analysis (HR = 1.033, [CI 1.006 -1.060], p = 0.017) but not on multivariate analysis. On univariate and multivariate analyses Gleason score (GS), number of positive nodes, and pretreatment PSA did not reach statistical significance for PFS or OS. Better than anticipated survival outcomes were demonstrated in cN1 prostate cancer patients treated with BT boost combined with EBRT and ADT. Future studies will compare these outcomes to matched patients treated without BT boost.