Finasteride in association with either flutamide or goserelin as combination hormonal therapy in patients with stage M1 carcinoma of the prostate gland. International Prostate Health Council (IPHC) Trial Study Group

Abstract

Background: It was very reasonable to consider that the combination of the 5alpha-reductase, finasteride, and a pure antiandrogen such as flutamide should provide an effective form of maximal androgen blockade (MAB). Finasteride decreases intraprostatic levels of 5alpha-dihydrotestosterone (DHT), and the antiandrogen would restrain the biological action of the residual DHT by interfering with its association with androgen receptor. This form of MAB should sustain the concentration of testosterone in plasma, thereby maintaining sexual function and reasonable quality of life. In order to investigate this, a randomized multicenter phase II clinical trial of patients with untreated M1 cancer of the prostate was developed and undertaken.

Methods: Patients were randomly allocated to one of three treatment schedules: 1) goserelin, 3.6 mg, s.c., monthly in combination with flutamide, 250 mg., t.i.d. and a placebo, daily, in the image of 2 x 5 mg finasteride; 2) goserelin, 3.6 mg., s.c., monthly in combination with finasteride, 10 mg (2 x 5 mg, daily) and a placebo (t.i.d.) in the image of flutamide; and 3) finasteride, 10 mg (2 x 5 mg, daily) in combination with flutamide (250 mg, t.i.d.). The reduction in concentration of serum PSA at 24 weeks was the endpoint of interest.

Results: Baseline prostate-specific antigen (PSA) levels of the patients in the three groups were very similar. There was a substantial decrease in levels of PSA in the three groups prior to the end of the study, the percent decrease in the groups being: 1) goserelin and flutamide combination, 99.1% (95% Confidence interval (CI), 97.7, 99.6); 2) goserelin and finasteride combination, 98.75% (95% CI, 97.1, 99.5); and 3) finasteride and flutamide combination, 97.6%, 95% CI, 94.5, 98.9). In the Generalized linear model (GLM) analysis, there was no center by treatment group interaction (P = 20), and there were no significant differences between centers (P = 0.059) nor among the three treatment groups (P = 0.16).

Conclusions: The decrease in levels of PSA in such a group of patients with M1 cancer of the prostate over a 24-week period was surprisingly large, and the differences in these decreased levels between the three treatment arms were remarkably small. There were no apparent differences in bone scan scores, World Health Organization (WHO) performance status, and pain scores between the arms. With regard to sexual function associated with quality of life, there were the understandable difficulties of data collection from patients treated with goserelin.