This systematic review aims to assess the efficacy of
aromatase inhibitors (AIs) in treating
pain symptoms caused by
endometriosis. A comprehensive literature search was conducted to identify all the published studies evaluating the efficacy of type II nonsteroidal
aromatase inhibitors (
anastrozole and
letrozole) in treating
endometriosis-related
pain symptoms. The MEDLINE, EMBASE, PubMed, and SCOPUS databases and the Cochrane System Reviews were searched up to October 2010. This review comprises of the results of 10 publications fitting the inclusion criteria; these studies included a total of 251 women. Five studies were prospective non-comparative, four were randomized controlled trials (RCTs) and one was a prospective patient preference trial. Seven studies examined the efficacy of AIs in improving
endometriosis-related
pain symptoms, whilst three RCTs investigated the use of AIs as post-operative
therapy in preventing the recurrence of
pain symptoms after surgery for
endometriosis. All the observational studies demonstrated that AIs combined with either
progestogens or
oral contraceptive pill reduce the severity of
pain symptoms and improve quality of life. One patient preference study demonstrated that
letrozole combined with
norethisterone acetate is more effective in reducing
pain and deep
dyspareunia than
norethisterone acetate alone. However,
letrozole causes a higher incidence of adverse effects and does not improve patients' satisfaction or influence recurrence of symptoms after discontinuation of treatment. A RCT showed that combining
letrozole with
norethisterone acetate causes a lower incidence of adverse effects and lower discontinuation rate than combining
letrozole with
triptorelin. Two RCTs demonstrated that, after surgical treatment of
endometriosis, the administration of AIs combined with
gonadotropin releasing hormone analogue for 6 months reduces the risk of
endometriosis recurrence when compared with
gonadotropin releasing hormone analogue alone. In conclusion, AIs effectively reduce the severity of
endometriosis-related
pain symptoms. Since
endometriosis is a
chronic disease, future investigations should clarify whether the long-term administration of AIs is superior to currently available endocrine
therapies in terms of improvement of
pain, adverse effects and patient satisfaction.