To evaluate for a possible testosterone surge during transition of therapy from degarelix to leuprolide.

We conducted an investigator-initiated, prospective, single-arm, open-label trial for evaluation of a potential testosterone surge during a transition of therapy from degarelix to leuprolide. Study patients were administered 3 monthly depot injections of degarelix, followed by one 3-month depot injection of leuprolide. A rise in serum testosterone was considered clinically relevant in previously castrate patients whose testosterone rose above 50 ng/dL.

Forty-five patients aged 59-86 years were included in the final analysis after completing the entire 6-month study. Nineteen percent of patients had received prior androgen deprivation therapy, and 10% had metastatic disease. Mean serum testosterone was reduced from a baseline of 374.6 ± 155.7 ng/dL to 16.5 ± 8.1 ng/dL, and prostate-specific antigen reduced from 23.8 ± 55.8 ng/mL to 1.6 ± 3.7 ng/mL after 3 months of treatment with degarelix. On transition from degarelix to leuprolide (day 90), there was a rise in testosterone from the nadir of 16.5 ng/dL to a peak of 25.8 ng/dL (P = .0005), occurring at day 93. Four patients (8.9%) experienced a testosterone surge with a mean peak serum testosterone of 80.7 ng/dL; all 4 returned to castrate levels within 7 days, and all remained asymptomatic throughout the testosterone fluctuation.

Fluctuations in serum testosterone after this transition of therapy were mild and short-lived with only 8.9% of men experiencing testosterone elevations to noncastrate levels.