Impact of Sequencing of Androgen Suppression and Radiation Therapy on Testosterone Recovery in Localized Prostate Cancer

Abstract

Purpose: We performed a secondary analysis of a phase 3 randomized trial to determine the influence of sequencing of radiation therapy and androgen deprivation therapy (ADT) on posttreatment testosterone recovery and implications of testosterone recovery on subsequent relapse.

Methods and materials: Patients with localized prostate cancer with Gleason score ≤7, clinical stage T1b to T3a, and prostate-specific antigen <30 ng/mL were randomized to neoadjuvant and concurrent ADT for 6 months starting 4 months before prostate radiation therapy (NHT arm) or concurrent and adjuvant ADT for 6 months starting simultaneously with radiation therapy (CAHT arm). Full testosterone recovery (FTR) was defined as recovery of testosterone to >10.5 nmol/L in patients with baseline ≥10.5 nmol/L or to baseline level in patients with baseline <10.5 nmol/L. Restricted mean survival time (RMST) since ADT initiation to supracastrate testosterone level (>1.7 nmol/L), and to FTR was compared between the arms using a truncation time point of 36 months.

Results: The adjusted difference in RMST to supracastrate testosterone between the CAHT and NHT arm was 1.5 months (95% confidence interval [CI], 0.5-2.5; P = .005). No difference was noted in RMST to FTR between the arms (18.7 vs 18.5 months, adjusted difference: 0.5; 95% CI, -1.4 to 2.4; P = .61). There was no evidence of heterogeneity of treatment effect (interaction P = .76) on risk of relapse over subgroups stratified by testosterone recovery to supracastrate level at 15 months after start of ADT. Based on a multistate Markov model, no independent effect of time to FTR on risk of subsequent relapse was observed (adjusted hazard ratio: 1.02; 95% CI, 0.96-1.08).

Conclusions: Patients should be counseled that an additional 12 months on average is needed for FTR to occur after treatment with prostate radiation therapy and 6 months of ADT. This is independent of the sequencing of ADT and radiation therapy. Furthermore, recovery of testosterone does not appear to affect the risk of subsequent relapse.