P-336 Efficacy of Gonadotrophin (GnRH) antagonists for endometriosis-associated pelvic pain - A systematic review and meta-analysis
Authors: Togobo M , Stocking K , Mohammed H , Saad A 
Published: July 2024

Abstract

Study question
Are Gonadotropin-releasing hormone (GnRH) antagonists effective and safe in managing pain associated with endometriosis?

Summary answer
GnRH antagonists seem effective and safe in managing endometriosis-associated pain for at least 12 weeks of use. There is uncertainty with the evidence.

What is known already
GnRH agonists are commonly used as effective second-line treatment for endometriosis-associated pain. However, these agonists have drawbacks and are not well-tolerated by many women. GnRH antagonists, offer potential advantages over the agonists while providing similar efficacy. They lack the initial stimulatory effects thereby avoiding the initial flare-up of symptoms, which is common with agonists. Furthermore, unlike agonists, which are mainly available as injections, the antagonist are also available as oral preparations, which allow titration of doses. In-vitro and animal studies have shown antagonists to induce regression of endometriotic lesions by apoptosis. However, their efficacy in relieving endometriosis-related pains remains uncertain.

Study design, size, duration
Extensive electronic search was conducted by the Cochrane Gynaecology and Fertility group, up to October 2023 to identify randomised controlled trials (RCTs) evaluating efficacy of GnRH antagonists in managing endometriosis-related pains compared with placebo and/or GnRH agonists. The main searched databases included CENTRAL, MEDLINE and EMBASE. Screening and selection of suitable studies were undertaken. Study eligibility criteria included treatment for ≥12 weeks, laparoscopically confirmed endometriosis and assessment of pelvic pain scores as the primary endpoint.

Participants/materials, setting, methods
Primary end-point was a change in endometriosis-related pain score after 12-week treatment with GnRH antagonists compared with placebo and/or GnRH agonists. Changes in pain and quality of life (QoL) scores and adverse-events of GnRH-antagonists were compared between the antagonist versus the agonist/placebo groups. Data were analysed using RevMan software (V5.4) to calculate the standard mean difference (SMD) for continuous data, and the risk ratios (RRs) with 95% confident intervals (95% CI) for categorical data.

Main results and the role of chance
Seven eligible RCTs (n = 3043) were included, all of which compared GnRH-antagonist versus placebo, and only three also compared versus GnRH-agonist (leuprorelin). The GnRH-antagonists included ASP1707, Elagolix, Linzagolix and Relugolix.
Meta-analysis of overall pelvic pain data from seven RCTs (n = 1684) showed significantly greater reduction in pain scores after 12 weeks of GnRH-antagonist versus placebo at low (SMD -0.29 95%CI -0.39 to -0.19; I2=0) and high doses (SMD-0.53 95%CI -0.63 to -0.43, I2=38%). Similarly, meta-analysis of other pains (dysmenorrhoea, non-menstrual pain, and dyspareunia) showed significantly greater pain score reduction with GnRH-antagonists versus placebo.
Meta-analysis of overall pelvic pain from two RCTs (n = 263) comparing GnRH-antagonist versus leuprorelin showed comparable reduction in pain scores after 12 weeks at low (SMD 0.33 95%CI 0.09 to 0.58, I2=44%) and high doses (SMD 0.06 95%CI -0.19 to 0.30, I2=0%). Similarly, meta-analysis of other forms of pain revealed comparable reductions of pain scores between both drugs.
Meta-analysis of QoL data (2RCTs, n = 259) revealed significantly greater improvements in scores with leuprorelin versus antagonists at low (SMD 0.74 95% CI 0.46 to 1.01; I2=98%) and high doses (SMD 0.35, 95%CI, 0.09 to 0.60, I2=97%).
The most frequently reported treatment-related side-effects were hot-flushes, headaches and nasopharyngitis. No life-threatening side-effects were reported.

Limitations, reasons for caution
There was high heterogeneity between studies (e.g. differences in antagonists and pain scoring systems). No information was provided on prior endometriosis surgery, which is a confounding factor. Additionally, declared COI by authors of all trials could introduce high risk of bias. Evidence certainty was therefore deemed low to very low.

Wider implications of the findings
GnRH-antagonists seem to offer a promising treatment for endometriosis-related pain, with comparable efficacy to the agonists, but with several potential advantages. However, given the low quality and uncertainty of the evidence in this meta-analysis, high quality RCTs with robust designs are needed before making any firm recommendations for clinical practice.

Trial registration number
not applicable