Importance: Unreported clinical trial results represent a violation of human rights. Oncology trials account for nearly 30% of interventional biopharmaceutical clinical studies registered on ClinicalTrials.gov and are the most numerous among all disciplines.
Objective: To analyze the reporting of results among all interventional oncology trials registered on ClinicalTrials.gov from 2007 through 2017.
Design, setting, and participants: This cohort study analyzed all clinical studies registered between June 1, 2007, and May 8, 2017, on ClinicalTrials.gov, the largest public clinical trial registry in the world. Trials with a recruitment status of completed or terminated and a primary completion date of on or before September 30, 2017, were selected. Data were analyzed between February 20, 2021, and February 26, 2021.
Main outcomes and measures: The main outcome was the percentage of trials that reported results either on ClinicalTrials.gov or in journal publications within 24 months of the primary completion date. Journal publication was ascertained by searching ClinicalTrials.gov for a link to the publication, PubMed using national clinical trial number, and Embase using national clinical trial number and filters.
Results: Of the 12 240 clinical trials registered in ClinicalTrials.gov, 7425 trials (60.7%; 95% CI, 60.0%-61.5%) reported results, with a 34.0% (95% CI, 30.3%-37.7%) increase in 24-month reporting rate from 2007 to 2017. Multivariable analyses confirmed that more recent trials (adjusted hazard ratio [HR], 1.11 per year increase; 95% CI, 1.10-1.13) and trials with larger sample sizes (51-100 patients: adjusted HR, 1.17 [95% CI, 1.09-1.24]; >100 patients: adjusted HR, 1.43 [95% CI, 1.33-1.54]) were more likely to report results. Terminated trials were less likely to report results compared with completed trials (adjusted HR, 0.88; 95% CI, 0.83-0.93). Compared with trials funded by industry, those funded by the National Institutes of Health were more likely to report results (adjusted HR, 1.39; 95% CI, 1.29-1.49), whereas those funded by other academic or nonprofit organizations were less likely to report results (adjusted HR, 0.66; 95% CI, 0.62-0.70). Among all 7425 trials, the results of 2807 trials (37.8%; 95% CI, 36.7%-38.9%) were posted only on ClinicalTrials.gov. These trials tended to be terminated early and to have small sample sizes (≤50 patients) compared with trials that published results in journals.
Conclusions and relevance: This study found a gradual improvement in results reporting among oncology trials over a 10-year period. Trial registries could serve as a results reporting platform for unpublished trials and as a data source of trial outcomes for future studies.