¹²⁵I Interstitial brachytherapy with or without androgen deprivation therapy among unfavorable-intermediate and high-risk prostate cancer

PURPOSE/OBJECTIVE(S): To determine if patients with unfavorable intermediate-risk (UIR), high-risk (HR), or very high-risk (VHR) prostate cancer (PCa) treated with ¹²⁵I interstitial brachytherapy benefit from androgen deprivation therapy (ADT). MATERIALS/METHODS: We reviewed our institutional database of patients with UIR, HR, or VHR PCa, per 2018 NCCN risk classification, treated with definitive ¹²⁵I interstitial brachytherapy with or without ADT from 1998−2017. Outcomes including biochemical failure (bF), distant metastases (DM), and overall survival (OS) were analyzed with the Kaplan-Meier method and Cox proportional hazards regression. PCa-specific mortality (PCSM) was analyzed with Fine-Gray competing-risk regression. RESULTS: Of 1033 patients, 262 (25%) received ADT and 771 (75%) did not. Median ADT duration was 6 months. By risk group, 764 (74%) patients were UIR, 219 (21%) HR, and 50 (5%) VHR. ADT was more frequently given to HR (50%) and VHR (56%) patients compared to UIR (16%; p<0.001), to older patients (p<0.001), corresponding with increasing PSA (p<0.001) and Grade Group (p<0.001). Median follow-up was 4.9 years (0.3−17.6 years). On multivariable analysis accounting for risk group, age, and year of treatment, ADT was not associated with bF, DM, PCSM, or OS (p≥0.05 each). CONCLUSION: Among patients with UIR, HR, and VHR PCa, the addition of ADT to ¹²⁵I interstitial brachytherapy was not associated with improved outcomes, and no subgroup demonstrated benefit. Our findings do not support the use of ADT in combination with ¹²⁵I interstitial brachytherapy. Prospective studies are required to elucidate the role of ADT for patients with UIR, HR, and VHR PCa treated with prostate brachytherapy.