Review question: Cochrane authors examined the evidence about aromatase inhibitors for subfertile women with polycystic ovary syndrome (PCOS).
Background: PCOS is the most common cause of infrequent or absent menstrual periods, and affects about 4% to 8% of women worldwide. It often causes anovulatory subfertility (subfertility related to failure to ovulate). Aromatase inhibitors are used to induce ovulation. Over the last ten years clinical trials have reached differing conclusions as to whether the AI letrozole is at least as effective for treating subfertility as the most commonly used treatment, clomiphene citrate.
Study characteristics: The review included 26 randomised controlled trials (RCTs) with 5560 women. In all trials the aromatase inhibitor used was letrozole. Comparators included clomiphene citrate, which was used in 17 of the RCTs, and laparoscopic ovarian drilling, which was used in three RCTs. Several studies included co-treatments in one or both arms.
Key results: Letrozole appears to improve live birth and pregnancy rates compared to clomiphene citrate. However the quality of this evidence was low and findings should be regarded with some caution.There appeared to be no difference between letrozole and laparoscopic ovarian drilling, though there were few relevant studies. OHSS was a very rare event and there were no occurrences in most studies. The evidence is current to September 2014.
Quality of the evidence: The overall quality of the evidence ranged from low to moderate.