A randomised study of GnRH antagonist (cetrorelix) versus agonist (busereline) for controlled ovarian stimulation: effect on safety and efficacy

OBJECTIVE: To assess safety and efficacy of cetrorelix utilisation in controlled ovarian stimulation (COS). STUDY DESIGN: Phase III, randomized, single center study of 131 patients undergoing COS and IVF with or without ICSI, in a University affiliated Hospital. Sixty-six patients were allocated to the protocol with antagonist and 65 to the agonist protocol arm. The Student's t-test, the Mann-Whitney test and the chi-square test were applied as required, using SPSS for Windows with a two-sided 5% significance level. RESULTS: The mean (+/-S.D.) duration of stimulation was 9.5+/-1.7 days in the antagonist group and 10.6+/-2.1 days in the agonist group (P=0.02). The mean (+/-S.D.) duration of suppression was 4.6+/-1.3 days in the antagonist group and 27.3+/-5.2 days in the agonist group (P<0.0001). No significant differences were noted in other outcome measures: amount of rFSH required, estradiol level on hCG day, number of follicles>or=15 mm and endometrial thickness on oocyte retrieval day, number of oocytes retrieved, fertilization rate and number of OHS cases. Clinical pregnancy rates per-attempt and per-transfer were 15.1% and 17.0% in the antagonist group and 16.9% and 20.0% in the agonist group (P=0.79 and 0.71, respectively). CONCLUSIONS: GnRH antagonists are an effective, safe and well tolerated alternative to agonists for COS.