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Lack of Transparency of Clinical Trials on Endometriosis

Guo, Sun-Wei MMed, PhD; Evers, Johannes L. H. MD, PhD

doi: 10.1097/AOG.0b013e318291f299
Original Research

OBJECTIVE: To estimate patterns of publication of clinical trials of endometriosis registered in and their associated characteristics.

METHODS: Information on interventional clinical trials on endometriosis that were registered at 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 nonindustry-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 (P<.001).

CONCLUSION: Despite mounting pressure on more transparency of clinical trials, the current state of transparency or lack thereof of clinical trials on endometriosis is worrisome and does not benefit the trial sponsor or the public. Thus, we again call for more transparency for endometriosis trials.


Among 35 completed trials on endometriosis, results were published for only 11 (31.4%), which is below the 66.3% reported in a recent survey of nonendometriosis trials.

Shanghai Obstetrics and Gynecology Hospital, Fudan University, Shanghai, China; and the Division of Reproductive Medicine and Biology, School for Oncology and Developmental Biology GROW, Maastricht University Medical Center, Maastricht, the Netherlands.

Corresponding author: Sun-Wei Guo, MMed, PhD, Shanghai Obstetrics and Gynecology Hospital, Fudan University, 419 Fangxie Road, Shanghai 200011, China; e-mail:

Supported by the National Science Foundation of China (grant number 81270676), the Shanghai Key Laboratory of Female Reproductive Endocrine-Related Diseases, and the Key Specialty Project of the Ministry of Health, China. The funding agencies had no role in the conception, design, or execution of this work.

Financial Disclosure Dr. Guo was a consultant to Bayer Schering Pharma and to Merck Serono Pharmaceuticals. Dr. Evers works in a department that receives two unrestricted research grants, unrelated to this study, from MSD Netherlands and Ferring Netherlands.

The authors thank Xin Wei for writing the C program and Yuedong Wang for suggesting the use of the bootstrap method and for assistance in the computation.

© 2013 by The American College of Obstetricians and Gynecologists. Published by Wolters Kluwer Health, Inc. All rights reserved.