Phase III Radiation Oncology Clinical Trials: A Snapshot of the Last Two Decades

Abstract

Modern radiation therapy is an integral modality in the treatment of cancer, yet data on the current state of Phase III radiation therapy trials remains scarce. We sought to characterize the landscape of radiation oncology phase III clinical trials in the last two decades. We searched ClinicalTrials.gov for phase III randomized controlled trials (RCTs) between 2003 and 2018. Randomized, multi-arm trials assessing a therapeutic intervention in adult cancer patients were included. Trials where radiation therapy was a main intervention were identified and grouped according to specific disease subsites and other trial information. Differences in trial factors between radiotherapy and other oncologic interventional trials were analyzed. Out of the 600 phase III RCTs identified, 15 trials were solely radiation therapy trials (2.5%). By disease subsite, we identified 3 (20%) breast cancer trials, 2 (13.3%) gastrointestinal cancer trials, 2 (13.3%) genitourinary cancer trials, 2 (13.3%) colorectal cancer trials, and 2 (13.3%) head and neck cancer trials. Radiation trials were less likely to be industry funded when compared to other oncological trials (20.0% vs 79.3% respectively, p<0.001). Furthermore, 73.3% of radiation trials had cooperative group sponsorship (vs 30.3% for other oncologic trials, p<0.001). Radiotherapy trials had less restrictions on including healthier patients (ECOG score 0 to 1) when compared to trials of systemic therapy (p<0.001). Even though radiation therapy is currently recognized as an integral modality in treating cancer patients, radiation therapy trials remain scarce and largely underfunded. Lastly, while cooperative groups seem to play an important role in radiation therapy trials, stakeholders are encouraged to assess and address ways to increase quality radiotherapy research.