Does nadir testosterone at the end of long term androgen deprivation therapy predict outcomes in high risk prostate cancer? Data from a phase III trial

London, England (UroToday.com) Dr. Nabid and colleagues presented their study this morning at the EAU 2017’s advanced prostate cancer poster session, assessing the impact of nadir testosterone on clinical outcomes after long-term androgen deprivation therapy (ADT) and radiation therapy (RT) for high risk prostate cancer. With emerging literature highlighting additional risks of ADT, including depression, cognitive decline, etc., this study is timely in assessing duration of ADT with regards to castrate testosterone levels and subsequent clinical outcomes.

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…

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