The significance of the trial outcome was associated with publication rate and time to publication.

OBJECTIVES: This study aims to comprehensively assess the publication of clinical trial results and factors associated with their publication.

STUDY DESIGN AND SETTING: Phase II and III trials of advanced breast cancer registered on ClinicalTrials.gov between October 1, 2000, and September 30, 2012, were identified. Publications were searched by using PubMed and reviewing those listed on the registry site. The main outcomes were publication rate, public availability of results, and time to publication.

RESULTS: Of 352 phase II and 74 phase III trials, 12.5% and 31.1% were published, whereas 46.9% and 58.1% had publicly available results, respectively. Compared to those with significant results, studies with nonsignificant results had delays in time to publication (P < 0.001). Even after adjusting for funding source and phase type, the significance of study outcomes was a significant factor that affected time to publication (hazard ratio = 6.02; 95% confidence interval: 3.59, 10.07; P < 0.001), with trials with significant outcomes taking less time to publish than those with nonsignificant outcomes.

CONCLUSION: Underreporting of results and nonpublication or delays in the publication of negative results were identified in registered trials of advanced breast cancer. Thus, further initiatives appear necessary to urgently address such publication bias.