Commentary: practicing on the tip of an information iceberg? Evidence of underpublication of registered clinical trials in oncology

Abstract

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.