The Long-Term Effect of Intensity-Modulated Radiation Therapy for Prostate Cancer on Testosterone Levels

Abstract Purpose Concerning about a long-term effect of the delivery of intensity-modulated radiation therapy (IMRT) for prostate cancer on serum testosterone levels remains unelucidated. We evaluated how IMRT for localized prostate cancer affects serum testosterone levels over a follow-up period of up to 10 years. Methods and Materials We retrospectively evaluated data from 182 patients with localized prostate cancer who underwent definitive IMRT alone between 2007 and 2014. Serum total testosterone (TT) levels were measured by blood draws between 6 AM and 11 AM prior to treatment and at every posttreatment follow-up for 10 years. Pretreatment and each posttreatment testosterone values were compared using a Wilcoxon signed-rank test. The dataset was stratified into 4 groups based on the pretreatment testosterone (pre-TT) values using quartiles. Results The median absolute or relative changes in TT levels from pretreatment were –0.42 ng/mL or -12.0% at 3 months after radiation therapy (P Conclusions Transient and modest decrease of TT levels after IMRT spontaneously recovered to the pretreatment levels at the 24- to 36-month time period, except in patients with higher quartile of pre-TT. This might be partly due to a variable sensitivity of individual testicular function to scattered radiation. Patients with lower pre-TT did not demonstrate a progressive overall rate of hypogonadism until 10 years following radiotherapy.