P-631 Extended letrozole regimen versus routine letrozole regimen in women with polycystic ovary syndrome undergoing their first ovulation induction cycle

Abstract

Abstract Study question Whether an extended letrozole regimen could result in a higher ovulatory rate than a routine regimen in PCOS women undergoing their first ovulation induction cycle. Summary answer PCOS women using the extended letrozole regimen failed to obtain a statistically higher rate of ovulation in comparison with the routine letrozole regimen. What is known already Letrozole has become the first-line agent for ovulation induction, however, nonresponsive cycles occurred in 10-58.8% of PCOS women during their ovulation induction therapy with letrozole alone. The extended letrozole regimen has been demonstrated to be a feasible method for inducing ovulation in those nonresponders. However, whether it could be applied to all the PCOS women as a first choice in the induction of ovulation remains to be explored. Study design, size, duration This is a prospective randomized controlled trial including 148 women with PCOS undergoing their first ovulation induction cycle with letrozole from January 2021 to October 2022. Participants/materials, setting, methods Participants were randomly assigned to receive an extended letrozole regimen (5 mg letrozole daily for 7 days) or a routine regimen(5 mg letrozole daily for 5 days) for one treatment cycle. Ovulation rate was the primary outcome. Secondary outcomes included the clinical pregnancy rate, the number of preovulatory follicles, the rate of multiple pregnancies. Main results and the role of chance The ovulation rate among women receiving a 7-day regimen was slightly higher than the rate with a 5-day regimen, but it did not reach a statistical significance in both the intention-to-treat analysis (90.54%[67/74]vs. 82.43%[59/74], P = 0.065) and per-protocol analysis (90.54%[67/74]vs. 84.29%[59/70], P = 0.257). The number of preovulatory follicles was nearly identical in the two groups (1.39±0.62 vs.1.37±0.59, P = 0.956), and no cases of ovarian hyperstimulation syndrome were observed. In the per-protocol analysis, the rates of clinical pregnancy (20.27%[15/74]vs.16.95%[10/70], P = 0.343) and live birth (13.51%[10/74]vs.11.43%[8/70], P = 0.976) did not differ significantly between treatment groups. Moreover, all the conceptions were singletons without neonatal defects. Limitations, reasons for caution The major concern of the current research is its single-centre and open label nature. Additionally, the limited number of lean PCOS women with a mean body mass index of 23-25 kg/m2 enrolled in our trial also restrict the generalizability of our findings. Wider implications of the findings Letrozole 5-day regimen remains to be the first choice for PCOS women undergoing ovulation induction therapy. Additional prospective trials with a larger sample size and different subgroups of PCOS are needed to assess the ovulatory effects of different letrozole treatment duration. Trial registration number ChiCTR2100042082