Unrecognized Kinetics of Serum Testosterone: Impact on Short-Term Androgen Deprivation Therapy for Prostate Cancer

PURPOSE: To evaluate the kinetics of serum testosterone (T) recovery following short-term androgen deprivation therapy (ADT), as the understanding thereof is essential for the proper management of prostate cancer (PCa), especially intermittent ADT. MATERIALS AND METHODS: This prospective analysis included male sex offenders who voluntarily received leuprolide acetate in order to alleviate sexual aberrance. Thirty-three and 25 patients who received 3 and 6 months of ADT were assigned to Group A and Group B, respectively. Serum T levels were obtained every week during the on-cycle period, then monthly during the off-cycle period for at least 12 months. RESULTS: The kinetics of serum T during the on-cycle period were similar in both groups. After flare reaction at week 2, a nadir of 0.45±0.29 ng/mL was achieved. In Group A, an abrupt rebound-upsurge was observed during the first 2 month off-cycle period, which surpassed the baseline level and reached a plateau level of 8.74±2.11 ng/mL during the flare (p<0.001). This upsurge was followed by a gradual decline back to baseline over the following 10 months. In Group B, a gradual increase was observed, and a baseline level of 7.26±1.73 ng/mL was reached at 5 months. Thereafter, an ongoing upsurge that surpassed baseline levels was observed until 12 months (8.81±1.92 ng/mL; p=0.002). CONCLUSION: The kinetics of serum T recovery during the off-cycle period varied according to the duration of ADT. Serum T should be monitored beyond normalization, as an excessive rebound may improve quality-of-life, but hamper the treatment efficacy of PCa.