Oncology Clinical Trials: Analysis of ClinicalTrials.gov

Noting a lack of data required to correctly identify the characteristics of current oncology trials and the ability of those trials to advance care, researchers recently conducted a comprehensive analysis of the national oncology clinical research portfolio. “Clinical trials are essential to cancer care,” the researchers commented, “and data about the current state of research in oncology are needed to develop benchmarks and set the stage for improvement.” They reported results of the analysis in JAMA Internal Medicine [2013;173(11):972-979].

ClinicalTrials.gov is the mandatory repository for information on most clinical studies conducted under US regulatory auspices. Recognizing the difficulty of accessing the complete, annotated data, members of the Clinical Trials Transformation Initiative created a high-quality, publicly available, searchable database: Aggregate Analysis of ClinicalTrials.gov (AACT).

Using Medical Subject Heading terms, the researchers identified all interventional clinical studies registered on ClinicalTrials.gov between October 2007 and September 2010. The studies were reviewed to validate classification, subcategorized by cancer type, and stratified by design characteristics to facilitate comparison across cancer types and other specialties.

During the study period, there were 40,970 studies registered; of those, 21.8% (n=8942) were oncology trials. Oncology was the single largest clinical area represented, followed by mental health, infectious disease, diabetes mellitus, and cardiology.

Oncology studies were more likely to be single arm (62.3% vs 23.8%; P<.001), open label (87.8% vs 47.3%, P<.001), and nonrandomized (63.9% vs 22.7%; P<.001) compared with non-oncology studies. Oncology trials were smaller than those of other clinical specialties (median 51 vs 72 patients; P<.001) and early-phase trials (phase 1 and/or 2) were more common in oncology (83.0% vs 51.6%; P<.001). Finally, oncology studies were more likely to have ongoing recruitment (60.7% vs 42.3%; P<.001) and were less likely to have reported completion of trials (10.7% vs 29.9%; P<.001) as of the end of the trial period.

The researchers further analyzed the data by cancer subset. Lung cancer, which has the highest incidence (14.5% of all new diagnoses) and the highest mortality (27.6% of all cancer deaths in 2010), was the focus of only 9.2% (n=824) of trials during the study period. Bladder cancer was the subject of only 1.1% of all trials, despite incidence and mortality rates of 4.6% and 2.6%, respectively.

The representation of breast cancer was proportionate to its incidence, despite a low ratio of incidence to mortality. The representation for lymphoma (6.6%) was higher than either its incidence or mortality (4.8% and 3.8%, respectively).

In breast cancer trials, 1 in 4 evaluated supportive care (9.6%), diagnosis (8.5%), or prevention (6.7%), whereas those categories account for less than 1 in 10 in pancreatic cancer trials.

The analyses of trial location and funding found that 65.1% of oncology trials included a North American study site and 34.9% were conducted purely in other regions. When the data were analyzed by cancer subtype, <50% were conducted only in North America for 5 of 10 subtypes. Across all oncology trials, 41.8% were funded by industry, 15.3% by government, and 42.9% by other funders (academic institutions, cooperative groups, and foundations).

The researchers concluded the report by stating, “There are significant variations between clinical trials in oncology and other diseases, as well as among trials within oncology. The differences must be better understood to improve both the impact of cancer research on clinical practice and the use of constrained resources.”