Prostate radiotherapy effects on testosterone levels: an empirical investigation

Abstract

There is a paucity of clinical data to support the hypothesis that external beam radiation therapy causes iatrogenic hypogonadism in prostate cancer patients. All prostate cancer patients treated at a single institution with radiation therapy between 2002 and 2010 were retrospectively evaluated. Patients treated with brachytherapy alone received 0 Gy of external beam radiation therapy and served as the control group. Patients treated with combination external beam radiation therapy + brachytherapy, or external beam radiation therapy alone were categorized into groups who received 45–54 Gy or > 60 Gy of external beam radiation therapy, respectively. Serum testosterone levels were routinely measured with prostate-specific antigen tests. The median follow-up periods for 149 evaluable patients in the control group (0 Gy), the 45–54 Gy group, and > 60 Gy group were 57, 62, and 55 months, respectively (p = 0.43). Among patients who underwent external beam radiation therapy, 53% were treated with intensity-modulated radiation therapy, 65% with pelvic lymph node coverage, and 78% with 18 megavoltage photons. There were no differences in serum testosterone level declines over time between the 45–54 Gy group (p = 0.32) or the > 60 Gy group (p = 0.14) when compared to the control group (0 Gy). While body mass index was associated with baseline testosterone levels in univariate analysis (p < 0.0001), it was not associated with the rate of change following radiation therapy (p = 0.6). Empirical evidence does not support the hypothesis that incidental exposure of the testicular Leydig cells from scattered photons and/or daily portal imaging affects testosterone levels.