Time to Prostate-specific Antigen Nadir and the Risk of Death From Prostate Cancer Following Radiation and Androgen Deprivation Therapy

Objective: To assess whether the time to prostate-specific antigen (PSA) nadir (TTN) has differential prognostic value in men who reach an undetectable vs detectable PSA nadir. Methods: Two hundred and four men from a prospective randomized controlled trial involving radiation therapy with or without 6 months of androgen deprivation therapy in unfavorable risk Prostate cancer (CaP) at academic or community based centers in Massachusetts, enrolled between 1995 and 2001. Adjusted hazard ratios (AHR) of the risk of CaP-specific mortality calculated using Fine and Gray competing risk regression. Results: After a median follow-up of 18.17years, 160 men died; 30 (18.75%) of CaP. Among men with a PSA nadir ≥ 0.2ng/ml, a TTN < median (12 months) was significantly associated with an increased CaP-specific mortality-risk vs the median or more (AHR 5.07, 95% CI 2.10-12.23, P <.001); whereas this association was not observed among men with a PSA nadir of < 0.2ng/mL, (AHR 9.9, 95% CI 0.23-433.8, P =.23). Conclusion: Men with both a short TTN and detectable PSA nadir could be considered for entry on randomized controlled trials at a novel entry point prior to PSA failure at the time of PSA nadir to completeplanned conventional androgen deprivation therapy vs that plus agent(s) shown to improve outcomes in men with or at high risk of having castrate-resistant CaP.