Assessing racial differences in time to subsequent treatment following androgen deprivation therapy among Veterans with prostate cancer

Background For metastatic and certain advanced prostate cancer (PC), guidelines support intensified androgen deprivation therapy (ADT) as first-line (1L) systemic treatment for improved outcomes. However, some patients receive ADT alone, leading to tumor progression requiring 2nd line therapy. Despite significant racial disparities in PC outcomes, there are no population-level studies assessing racial differences in time to subsequent treatment after 1L ADT. Methods We performed a retrospective population-level analysis to assess the association between race and time to subsequent treatment after ADT in the Veterans Affairs Health Care System. Primary outcome was time from ADT monotherapy to subsequent treatment, defined as receipt of androgen receptor pathway inhibitor (ARPI), non-steroidal first-generation anti-androgen (NSAA), chemotherapy, or other treatments. We used Cox models and Kaplan-Meier (KM) analyses to estimate subsequent treatment rates by Non-Hispanic White [NHW], Non-Hispanic Black [NHB], Hispanic and Other patients adjusted for baseline covariates. Results From 2001–2021, 141,495 PC patients received ADT alone. During median (IQR) follow-up of 51.1 (22.8, 97.2) months, 28,144 patients (20%) had subsequent treatment: 11,319 (40%) ARPIs, 12,990 (46%) NSAAs, 3,402 (12%) chemotherapy and 433 (2%) other 2nd line therapies. NHB had significantly lower subsequent treatment rates (HR = 0.82, 95%CI = 0.80–0.85) compared to NHW. Both Hispanic (HR = 0.93, 95%CI = 0.88–0.98) and Other men (HR = 0.91, 95%CI = 0.84–0.98), also had lower subsequent treatment rates. Conclusions All races examined had significantly lower rates of subsequent treatment after 1L ADT relative to NHW. Further investigation is needed to determine if these lower rates of subsequent treatment reflect lower rate of progression or undertreatment of progressing patients.