This cohort included 630 patients with high risk prostate cancer undergoing RT who were randomized to receive either 18 or 36 months of goserelin. Castrate levels of testosterone were sub-stratified as ≤0.7 (≤20 ng/dL – surgical castration), 0.7-1.7 (>20-<50 ng/dL – medical castration), and ≥1.7 nmol/L (≥50 ng/dL – castration not reached). Among the testosterone groups, there were balanced baseline characteristics (age, performance status, PSA, stage, duration of ADT), however patients with testosterone ≤0.7 nmol/L had a higher proportion of patients with Gleason 8-10 disease. At the end of pre-specified ADT duration, 89.2% of patients achieved a testosterone level <1.7 nmol/L. After more than 9 years of follow-up, 30% of patients experienced biochemical failure, 13% prostate cancer recurrence, 8% castration-resistance, and 41% of patients died. Of note, there was no difference in these clinical outcomes between the nadir testosterone level groups, which was confirmed on multivariate Cox proportional regression modeling. A limitation of this study is that nadir testosterone was missing for 28% of patients.
Dr. Nabid and colleague’s study shows that our goal for testosterone nadir after ADT among men with high risk prostate cancer undergoing concomitant RT should be <1.7 nmol/L, regardless of ADT duration. Allowing clinicians to safely discontinue ADT earlier after achieving testosterone levels <1.7 nmol/L will hopefully diminish debilitating physical and psychological side effects associated with ADT.
Presented by: Abdenour Nabid, Department of Radio-Oncology, Centre Hospitalier Universitaire de Sherbrooke, Sherbrooke, Canada
Written by: Zachary Klaassen, MD, Urologic Oncology Fellow, University of Toronto
at the #EAU17 -March 24-28, 2017- London, England