Time to Prostate-Specific Antigen Nadir After Androgen Suppression Therapy for Postoperative or Postradiation PSA Failure and Risk of Prostate Cancer-Specific Mortality

Objectives: To examine whether the time to the prostate-specific antigen (PSA) nadir was associated with prostate cancer-specific mortality (PCSM) in men with PSA failure after radical prostatectomy or radiotherapy who do not achieve an undetectable PSA level (PSA level of 0.2 ng/mL or less) after 8 months of androgen suppression therapy (AST). Methods: The cohort included 162 men with localized prostate cancer treated with AST for an increasing PSA level after radical prostatectomy or radiotherapy. Gray's analysis was used to evaluate for an association between the time to PSA nadir after 8 months of AST and the time to PCSM, adjusting for established prognostic factors. The median age and follow-up after 8 months of AST was 71.2 and 1.8 years, respectively. Results: After adjusting for Gleason score, pre-AST PSA doubling time, PSA at AST, PSA nadir value, time to PSA failure, initial treatment, and age, the time to PSA nadir was significantly associated with PCSM (adjusted hazard ratio 2.53, 95% confidence interval 1.24 to 5.14, P = 0.01). Men with a PSA nadir greater than the median value of 0.9 ng/mL and the time to PSA nadir longer than the median of 4 months had significantly greater PCSM estimates (P <0.001) compared with men with a PSA nadir of 0.9 ng/mL or less. Conclusions: The time to PSA nadir, combined with the PSA nadir level, can be used to identify men who are at high risk of PCSM after a short course of AST for entry onto clinical trials using novel systemic agents with AST.