A randomized comparison of the clinical and hormonal effects of two GnRH agonists in patients with prostate cancer.

Objective: The aims of the study were (i) to compared the efficacy of the two long-acting GnRH agonists (GnRHa) triptorelin (Trp) and leuprolide (Leu) in men with prostate cancer and (ii) to assess the pattern of plasma testosterone levels following each injection of GnRHa.

Patients And Methods: 67 patients referred for prostate cancer not suitable for surgery were randomly allocated to two treatment regimens: 33 patients received 3.75 mg Trp i.m. at 4-week intervals for 3 months and 34 patients were treated with 3.75 mg Leu s.c. at the same rhythm of administration for 3 months.

Results: Clinical data at entry and assessed monthly during follow-up did not differ between the two groups. Plasma prostate-specific antigen (PSA) and testosterone were measured before, 24 and 72 h after each injection of GnRHa. During treatment, PSA dropped similarly in both groups. By month 2, testosterone was < 1.0 nmol/l in 77 and 48% of patients treated with Trp and Leu, respectively (p = 0.02). 24 and 72 h after GnRHa injection, 77 (Trp) and 56% (Leu) of patients had testosterone < 1.0 nmol/l (p < 0.05).

Conclusions: The second and third injections of GnRHa were not followed by a significant increase in testosterone. Trp induced a higher decrease in testosterone than did Leu. The implications in terms of survival should, however, be studied in a larger and longer study.