Objectives: To investigate whether testosterone surges occur on repeat injections of 3.6 or 10.8 mg goserelin (Zoladex) depot and, if so, their extent.
Methods: Men with prostate cancer for whom hormonal therapy was indicated were randomized to open-label goserelin 3.6 mg every 28 days (n = 129) or 10.8 mg every 84 days (n = 118) for 48 weeks. Serum testosterone and luteinizing hormone levels were measured before repeat injection on day 1 of each treatment cycle and then on days 4 and 8. Surges were defined in three ways: type 1, simultaneous increase in both testosterone and luteinizing hormone to within the age-specific normal range; type 2, increase in testosterone to within the age-specific normal range; and type 3, elevation in testosterone from less than to greater than the castrate level (greater than 18.5 ng/dL).
Results: Most patients did not experience a testosterone surge. Two patients (1.8%) in the 10.8-mg group had a type 1 surge after one repeat injection and two (1.6%) in the 3.6-mg group had a type 2 surge after one repeat injection. Type 3 surges occurred after one or more repeat injections in 34 (27.0%) and 20 (17.7%) patients in the 3.6-mg and 10.8-mg groups, respectively (P = 0.065); the mean surge (+/- standard deviation) was 11.2 ng/dL (+/-13.5) and 17.3 ng/dL (+/-24.6), respectively. No patient with a testosterone surge had clinical symptoms of a tumor flare reaction.
Conclusions: The testosterone levels were consistently maintained within the castrate range (18.5 ng/dL or less) in most (77.4%) patients receiving long-term 3.6 mg or 10.8 mg goserelin.