A Nomogram for Testosterone Recovery After Combined Androgen Deprivation and Radiation Therapy for Prostate Cancer

Purpose Testosterone recovery (TR) after androgen deprivation therapy (ADT) and radiation therapy (RT) is not well characterized. We studied TR in men who received RT and either short-term ADT (STADT) or long-term ADT (LTADT) and aimed to create a nomogram to predict TR. Methods and Materials We identified consecutive localized prostate cancer patients treated with ADT-RT at 2 academic medical centers from January 2011 to October 2016 with documented baseline testosterone. TR was time from last ADT injection to testosterone normalization. The Kaplan-Meier method was used to estimate time to TR. Cox proportional hazards models identified TR predictors. A nomogram was trained with site 1 and externally validated with site 2. Results A total of 340 patients were included; 69.7% received STADT for a median duration of 6 months; 30.3% received LTADT for a median duration of 24.3 months. Median follow-up was 26.7 months. Median time for TR was 17.2 months for STADT and 24.0 months for LTADT patients ( P  = .004). The 2-year cumulative incidence of TR was 53.1% after LTADT versus 65.7% after STADT ( P  = .004). On multivariate analysis, shorter duration ADT (hazard ratio [HR], 0.96; P  = .004), higher pretreatment testosterone (HR, 1.004; P P  = .002) were associated with shorter time to TR. Older age (HR, 0.97; P  = .09) and white race (HR, 0.67; P  = .06) trended as longer TR predictors. A nomogram was generated to predict probability of TR at 1, 2, and 3 years. The concordance index was 0.71 (95% confidence interval, 0.64-0.78) for the validation cohort. Conclusions In this population of localized prostate cancer patients, TR after ADT-RT was variable. Using baseline testosterone, ADT duration, body mass index, age, and race, a predictive nomogram can estimate the likelihood of TR.