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Commentary

Commentary: Practicing on the Tip of an Information Iceberg? Evidence of Underpublication of Registered Clinical Trials in Oncology

^aFred Hutchinson Cancer Research Center, Seattle, Washington, USA; Departments of ^bMedicine and ^cHealth Services, University of Washington, Seattle, Washington, USA

Key Words. Cancer • Clinical trials • Registries • Publication bias

Correspondence: Scott D. Ramsey, M.D., Ph.D., Fred Hutchinson Cancer Research Center, 1100 Fairview Avenue North M3-B232, PO Box 19024, Seattle, Washington 98109, USA. Telephone: 206-667-7846; Fax: 206-667-5977; e-mail: sramsey{at}fhcrc.org

Received June 13, 2008; accepted for publication June 30, 2008.

Disclosure: Employment/leadership position: None; Intellectual property rights/inventor/patent holder: None; Consultant/advisory role: None; Honoraria: None; Research funding: National Cancer Institute R25 CA 92408; Ownership interest: None; Expert testimony: None; Other: None. The content of this article has been reviewed by independent peer reviewers to ensure that it is balanced, objective, and free from commercial bias. No financial relationships relevant to the content of this article have been disclosed by the authors, planners, independent peer reviewers, or staff managers of the article.

Objective. Members of the International Committee of Medical Journal Editors require, as a condition of consideration for publication, that all clinical trials be registered in a public trials registry. We evaluated the proportion of registered trials that are published in the peer-reviewed literature.

Methods. After downloading the contents of the National Institutes of Health's ClinicalTrials.gov registry, we used key words to identify trials in oncology. We then evaluated the proportion of trials that had been published in journals listed in PubMed.gov. Among trials with published results, we determined the proportion that reported positive versus negative results.

Results. Among the 2,028 trials meeting the inclusion criteria, 17.6% were available in PubMed. Twenty-one percent of the trials registered before September 1, 2004 were published, compared with 11.9% of those registered after this date. Trials sponsored by clinical trial networks published the greatest proportion of registered studies (59.0%); studies sponsored by industry published the fewest (5.9%). Among published studies, 64.5% reported the results as positive findings.

Conclusions. Less than one in five studies in cancer that are registered with clinicaltrials.gov have been published in peer-reviewed journals. Research sponsors, researchers, and journal editors should redouble their efforts to encourage publication of registered clinical trials in oncology.

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