Cancer randomized trials showed that dissemination bias is still a problem to be solved

The objective of the present study was to determine the publication rate of cancer randomized controlled trial (RCTs) and to analyze the determinants of the publication, as well as to estimate the possible existence of a location and time lag bias. We also described the bibliometric characteristics of the publications.

We conducted an observational study that identified publications resulting from RCTs involving cancer-related drug products. These studies were authorized and registered by the Spanish Agency of Medicines and Medical Devices between 1999 and 2003.

We identified 168 publications of 303 RCTs, resulting in a publication rate of 55.4% after a mean follow-up of 12 years. The only factor associated to the likelihood of nonpublication was the study setting favoring only national RCTs (odds ratio 2.7; 95% confidence interval 1.5-4.8). Type of sponsor did not seem to be associated, although the largest volume of nonpublished trials is international, industry-sponsored. Positive results seemed to be associated to a publication in a higher impact factor journal and a shorter time-to-publication.

About half of the cancer RCTs during the target period have not been published. The national setting is a factor associated to nonpublication, whereas the direction of results determines its dissemination (impact factor and timely publication).