Evaluating the landscape and characteristics of endometriosis research published between 1990 and 2024

We aimed to assess the landscape of endometriosis randomised-controlled trials (RCTs) between 1990 and 2024 by characterising RCTs by management type, primary outcome, country of origin, trial registration, sample size and minimum detectable difference based upon standard RCT power targets of 80% and 90%.

We identified all endometriosis RCTs from Dimensions.AI with an English abstract. Articles were examined for sample size, theme and primary outcome. Sample sizes were used to calculate minimum detectable effect size (MDES) of studies at 80% and 90% power.

We analysed 536 RCTs using 'R'. 55.6% (N = 298) of studies investigated medical management of endometriosis, of which 177 investigated Gonadotrophin Releasing Hormone (GnRH) analogues. RCTs investigating complementary therapies rose from 0.847% (N = 1) in 1990-1999 to 28.7% (N = 31) of medical management RCTs in 2020-2024. The US and China led publishing with 70 and 65 RCTs total, respectively. Importantly, of 445 RCTs with at least one continuous outcome, we found that at 90% power, 55.7% (N = 248) of RCTs would only detect a standardised mean difference which was 'large' or greater.

We noted several trends within endometriosis RCTs. In line with wider literature, China accounts for a growing proportion of RCTs. Although complementary therapy is increasingly recognised as a management option requiring further research, most medical management RCTs focussed on GnRH analogues as part of their treatment regime despite these being considered second-line management options. A high proportion of RCTs was underpowered to detect potentially clinically significant effects of intervention-potentially indicating significant resource wastage.