Background: To date, research has not determined the optimal procedure for adjuvant androgen deprivation therapy (ADT) in patients with locally advanced prostate cancer (PCa) treated for 6 months with neoadjuvant ADT and external-beam radiation therapy (EBRT).
Methods: A multicenter, randomized, phase 3 trial enrolled 303 patients with locally advanced PCa between 2001 and 2006. Participants were treated with neoadjuvant ADT for 6 months. Then, 280 patients whose prostate-specific antigen levels were less than pretreatment levels and less than 10 ng/mL were randomized. All 280 participants were treated with 72 Gy of EBRT in combination with adjuvant ADT for 8 months. Thereafter, participants were assigned to long-term ADT (5 years in all; arm 1) or intermittent ADT (arm 2). The primary endpoint was modified biochemical relapse-free survival (bRFS) with respect to nonmetastatic castration-resistant prostate cancer (nmCRPC) progression, clinical relapse, or any cause of death.
Results: The median follow-up time after randomization was 8.2 years. Among the 136 and 144 men assigned to trial arms 1 and 2, respectively, 24 and 30 progressed to nmCRPC or clinical relapse, and 5 and 6 died of PCa. The 5-year modified bRFS rates were 84.8% and 82.8% in trial arms 1 and 2, respectively (hazard ratio, 1.132; 95% confidence interval, 0.744-1.722).
Conclusions: Although modified bRFS data did not demonstrate noninferiority for arm 2, intermittent adjuvant ADT after EBRT with 14 months of neoadjuvant and short-term adjuvant ADT is a promising treatment strategy, especially in a population of responders after 6 months of ADT for locally advanced PCa.
Keywords: castration-resistant prostate cancer; external-beam radiation therapy; intermittent androgen deprivation therapy; prostate cancer; prostate-specific antigen (PSA).
© 2020 American Cancer Society.