Lack of Transparency of Clinical Trials on Endometriosis

OBJECTIVE: To estimate patterns of publication of clinical trials of endometriosis registered in ClinicalTrials.gov and their associated characteristics. METHODS: Information on interventional clinical trials on endometriosis that were registered at ClinicalTrials.gov and updated as having been completed by October 25, 2012, was retrieved and the publication status and time to publication in Medline-indexed journals were ascertained by searching PubMed and by sending e-mail inquiries to the principal investigators listed by the registry. RESULTS: Seventy-one interventional trials of endometriosis, testing various drugs and biologicals, were identified. Among them, 49.3% (35/71) were completed by October 25, 2012, 21.1% were either stopped or inactive in the past 2 years, and the remaining 29.6% were ongoing. Among the 35 completed trials, 25 (71.4%) were sponsored by industry and results were published for only 11 (31.4%; five industry-sponsored, and six non-industry-sponsored). Trials sponsored by industry were nearly four times less likely to publish their results than nonindustry-sponsored trials, even though these trials typically had larger sample sizes and were completed faster. Compared with the publication rate of 20% found 4 years ago, the current rate has increased only marginally but still lies significantly below the reported 66.3% surveyed recently among 546 completed nonendometriosis trials registered at ClinicalTrials.gov (P