Does Baseline Serum Testosterone Influence Androgen Deprivation Therapy Outcomes in Hormone Naïve Patients with Advanced Prostate Cancer?

Abstract

To study baseline serum testosterone's prognostic value in hormone naïve advanced prostate cancer patients receiving continuous androgen deprivation therapy. The study population undergoing continuous androgen deprivation therapy (agonist or antagonist) with 1-year followup was pooled for post-hoc analysis from 2 large prospective, randomized, parallel arm phase 3b trials (NCT00295750-Global; NCT00928434-USA). Survival end points were evaluated for baseline serum testosterone effect as a continuous variable and compared for low (less than 250 ng/dl) vs normal (250 ng/dl or greater) groups based on the saturation model, using Kaplan-Meier survival estimates, log rank test, and Cox proportional hazards regression models incorporating established clinically important baseline factors. On intention to treat analysis 138 (16.5%) of 838 eligible men had baseline serum testosterone less than 250 ng/dl. Key cancer characteristics for low vs normal baseline serum testosterone cohorts were comparable; Gleason sum 7-10 (55% vs 58%), stage and prostate specific antigen 20 ng/ml or greater categories (38% each). The lowest baseline serum testosterone quartile cutoff value was 282 ng/dl or less (206 patients). Multivariable analysis showed a significant baseline serum testosterone effect for all survival end points. For the saturation model low cutoff less than 250 ng/dl, significance remained for overall (HR 2.24; p <0.02) and progression-free survival (HR 1.57; p <0.02), but not for time to prostate specific antigen progression (HR 1.37; p=0.2). Lower baseline serum testosterone was significantly associated with worse study survival end points in hormone naïve advanced prostate cancer patients undergoing continuous medical castration. Future well-designed studies should compare continuous androgen deprivation therapy (the current gold standard) with newer alternatives to optimize individualized management in these men.