Treatment of endometriosis in different ethnic populations: a meta-analysis of two clinical trials

Endometriosis is a chronic, painful disease caused by the growth of endometrial-like tissue outside the uterus, which induces a chronic inflammation resulting in fibrosis, adhesion formation, and scarring around the abdominal cavity and organs [1,2]. Endometriosis is common, occurring in approximately 10% of women of reproductive age [3], although the exact prevalence remains unknown because invasive procedures are required to confirm the diagnosis. Limited evidence suggests that the prevalence of endometriosis may vary with ethnicity. A slightly higher prevalence is reported in Japanese and other Asian women, and a lower incidence among African women, when compared to Caucasians [4-7]. Ethnic variations in prevalence could result from divergence in a range of genetic and environmental risk factors, which are thought to underlie the development of this complex condition [8-12]. Regardless of ethnicity, the symptoms of endometriosis are highly variable between individual women and often overlap those of other conditions. In many women, the symptoms are severe and quality of life can be greatly reduced [13-15].Treatment approaches vary widely between regions worldwide, reflecting in part the availability of approved medications and divergences in surgical practice. In Japan, for example, gonadotropin-releasing hormone (GnRH) analogues appear to be widely used [16], while progestins account for a relatively small proportion of treatment regimens [17]. In other parts of the world, combined oral contraceptives and non-steroidal anti-inflammatory drugs are widely prescribed for relief of endometriosis-related pain, despite limitations in the supportive trial evidence, and the androgen, danazol, is still used in a number of countries despite its unpleasant side effects [18].Progestins have been prescribed for the treatment of endometriosis for a number of decades, although the availability and actual use of approved progestins vary markedly between regions. The older proge