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 (1 L) systemic treatment. However, some patients receive ADT alone, leading to tumor progression requiring 2 line therapy. Despite racial disparities in PC outcomes, there are no population-level studies assessing racial differences in time to subsequent treatment after 1 L 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 competing risks 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, 3402 (12%) chemotherapy and 433 (2%) other 2 line therapies. NHB had significantly lower subsequent treatment rates (HR = 0.82, 95% CI = 0.80-0.85) vs. 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. When stratified by age, associations between race/ethnicity and time to subsequent treatment were stronger in younger patients.

[CONCLUSIONS] All races examined had significantly lower rates of subsequent treatment after 1 L ADT relative to NHW, especially in younger patients. Further investigation is needed to determine if these lower rates of subsequent treatment reflect lower rate of progression or undertreatment of progressing patients.