Duration of androgen deprivation therapy and nadir of testosterone at 20 ng/dL predict testosterone recovery to supracastrate level in prostate cancer patients who received external beam radiotherapy

Abstract

Objectives: To determine the predictors of testosterone recovery after termination of androgen deprivation therapy in high/intermediate-risk prostate cancer patients receiving external beam radiation therapy with neoadjuvant and adjuvant androgen deprivation therapy.

Methods: A total of 82 patients who underwent external beam radiation therapy with androgen deprivation therapy for prostate cancer were retrospectively analyzed. Serum testosterone levels after androgen deprivation therapy terminations were studied. Cox proportional hazard models and the Kaplan-Meier method were used for statistical analysis.

Results: Median age, baseline testosterone, nadir testosterone and duration of androgen deprivation therapy were 73 years, 456 ng/dL, 16 ng/dL and 26 months, respectively. Androgen deprivation therapy duration of 33 months (hazard ratio 0.13; P = 0.0018), nadir testosterone of 20 ng/dL (hazard ratio 0.35; P = 0.0112) and testosterone >50 ng/dL at 6 months after androgen deprivation therapy termination (hazard ratio 0.21; P = 0.0075) were significantly associated with testosterone recovery to normal levels (200 ng/dL) on multivariate analysis. Androgen deprivation therapy duration of 33 months (hazard ratio 0.31; P = 0.0023) and nadir testosterone of 20 ng/dL (hazard ratio 0.38; P = 0.0012) were significantly associated with testosterone recovery to the supracastrate level (50 ng/dL) on multivariate analysis. After dividing patients into three risk groups, the rate of testosterone recovery to the normal level after 2 years of androgen deprivation therapy termination was 100% in the low-risk group versus 20.8% in the high-risk group (P < 0.0001); the rate of testosterone recovery to the supracastrate level was 100% in the low-risk group versus 51.5% in the high-risk group (P < 0.0001).

Conclusions: Duration of androgen deprivation therapy and achievement of nadir testosterone 20 ng/dL both predict testosterone recovery to the supracastrate level in prostate cancer patients undergoing external beam radiation therapy with androgen deprivation therapy.

Keywords: androgen deprivation therapy; nadir testosterone; prostate cancer; radiation therapy; testosterone recovery.