Are combined hormonal contraceptives the neglected treatment for symptomatic endometriosis? - Fertility and Sterility

I want a new drug. An approximate answer to the right question is worth a great deal more than a precise answer to the wrong question. There is good and bad news for women needing medical treatment for endometriosis. The good news is that, based on the results of the systematic review conducted by Jensen and coworkers (1x1Jensen, J.T., Schlaff, W., and Gordon, K. The use of combined hormonal contraceptives for the treatment of endometriosis-related pain: a systematic review of the evidence. Fertil Steril. 2018; 110: 136–151 Abstract | Full Text | Full Text PDF | Scopus (6) | Google ScholarSee all References)(1), “combined hormonal contraceptives (CHC) treatment, administered cyclically or continuously, results in clinically important and statistically significant reductions from baseline in endometriosis-related pain” and “CHC treatment also resulted in improvements from baseline in quality of life in most studies that measured this outcome.” The bad news is that the data supporting the use of CHC were judged of low quality, mainly due to nonrandom allocation of treatments, absence of treatment concealment, and lack of a placebo arm in most studies. Why are data on CHC for endometriosis still of “low quality,” whereas those on GnRH agonists and antagonists and dienogest are considered of “high quality”? A tentative answer is that pharmaceutical industries, which have the organization and money to conduct costly double-blind, placebo-controlled, multicenter, randomized controlled trials (RCTs), have limited interest in CHC as a treatment for endometriosis, whereas independent investigators interested in CHC struggle with the overwhelming administrative and financial burden associated with the planning of such RCTs. Therefore, research groups without industry support either take the long and winding road to public funding or choose observational designs that provide low-quality evidence. In fact, of the 18 included studies in the Jensen et al. review, only five were fully or partly industry sponsored, whereas the remaining 13 (72%) were conducted by independent groups without industry support. Only one RCT was funded by the National Institutes of Health (1x1Jensen, J.T., Schlaff, W., and Gordon, K. The use of combined hormonal contraceptives for the treatment of endometriosis-related pain: a systematic review of the evidence. Fertil Steril. 2018; 110: 136–151 Abstract | Full Text | Full Text PDF | Scopus (6) | Google ScholarSee all References)(1). Pharma industries are unlikely to invest in CHC for endometriosis because the extra revenues from this