Prostate radiotherapy effects on testosterone levels: an empirical investigation

Abstract

ObjectiveThere is a paucity of clinical data to support the hypothesis that external beam radiation therapy causes iatrogenic hypogonadism in prostate cancer patients.MethodsAll prostate cancer patients treated at a single institution with radiation therapy between 2002 and 2010 were retrospectively evaluated. Patients treated with brachytherapy alone received 0Gy 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 45-54Gy or >60Gy of external beam radiation therapy, respectively. Serum testosterone levels were routinely measured with prostate-specific antigen tests.ResultsThe median follow-up periods for 149 evaluable patients in the control group (0Gy), the 45-54Gy group, and >60Gy group were 57, 62, and 55months, 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 45-54Gy group (p=0.32) or the >60Gy group (p=0.14) when compared to the control group (0Gy). 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).ConclusionEmpirical 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.