Publication of interventional phase 3 and 4 clinical trials in radiation oncology: an observational study

Clinical trials produce the best data available for decision-making in modern evidence-based medicine. We aimed to determine the rate of non-publication of interventional phase 3 and 4 clinical trials involving patients with cancer undergoing radiotherapy.

The ClinicalTrials.gov database was searched for interventional phase 3 and 4 trials in radiotherapy with a primary completion date before 1 January 2013. We determined how many of these registry entries have not published the compulsory deposition of their results in the database and performed a systematic search for published studies in peer-reviewed journals.

Of 576 trials, 484 (84.0%) did not deposit a summary result in the registry. In addition, 44.9% of them did not publish their results in a peer-reviewed journal. Similar percentages were found for most cancer subtypes: brain (41%), breast (38%), cervical (66%), colorectal (38%), lung (48%), prostate (45%), bladder (56%), head and neck (56%) and lymphoma (33%).

Our results show that most trials in radiation oncology did not report the results in the registry. Almost half of these trials have not been published in the biomedical literature. This means that a large number of study participants were exposed to the risks of trial participation without the supposed benefits that sharing and publishing of results would offer to future generations of patients.