Progestins for symptomatic endometriosis: a critical analysis of the evidence

To obtain estimates of the effects of progestin treatment for pelvic pain associated with endometriosis.

Information from studies published in the English-language literature between 1966 and 1996 was pooled. Articles were identified through hand and computerized searches using MEDLINE.

A total of 27 trials that were published in peer-reviewed journals were identified, and 13 of these were excluded from the analysis because of methodologic limitations. Nine of the remaining 14 studies were noncomparative (8 prospective and 1 retrospective), 1 was quasi-randomized, and 4 were true randomized controlled trials.

The sample size was generally limited; the mean number of patients included was 26 in the noncomparative trials and 29 in the randomized controlled trials. The mean duration of treatment was 6 months. A total of 355 women had pain at entry. Considering all noncomparative studies, the pooled frequency of nonresponders at the end of treatment was 9% (18/203; 95% confidence interval [CI], 5.3% to 13.6%). The common odds ratio from the four randomized controlled trials comparing progestins with danazol or a GnRH agonist was 1.1 (95% CI, 0.4 to 3.1), suggesting equivalence in treatment effect. In the only double-blind, placebo-controlled trial, the frequency of nonresponders was not significantly different in the two arms. Only four studies assessed pain after drug withdrawal. The pooled frequency of pelvic pain at the end of follow-up was 50% (35/70; 95% CI, 37.8% to 62.2%). The overall crude conception rate after therapy among women who desired pregnancy was 44% (86/194; 95% CI, 37.2% to 51.6%). Side effects of limited clinical relevance were observed frequently.

The available data suggest that the efficacy of progestins for temporary relief of endometriosis-associated pelvic pain is good and comparable to that of other, less safe treatments.