A new study of cancer clinical trial participation breaks down and analyzes the reasons why only a small fraction of adult cancer patients participate in research.

The study found that a main reason why so few people participate is because there is no trial for more than half of cancer patients for their particular type and stage of cancer.1

“Going back to studies in the 1990s and early 2000s, researchers frequently cite the statistic that less than 5% of adult cancer patients participate in clinical trials,” says Joseph Unger, PhD, health services researcher and biostatistician at Fred Hutchinson Cancer Research Center in Seattle.

“But, in fact, when patients are offered to participate in a trial, about half choose to do so,” he adds. “This leaves a very different impression about the role of patients in clinical trial participation, indicating that they are much more willing to participate than is commonly assumed.”

Other systemic, structural reasons why people fail to participate have to do with clinical trial locations and the cost of travel, as well as the fact that cancer patients often are ineligible for trial enrollment.

“Many patients cannot travel to where the trials are available because of the constraints like taking time off work, family constraints, and child care,” he says.

Traveling for clinical trials also is expensive with travel costs, housing/hotels — sometimes for long periods of time — and other costs related to living in one place and maintaining a residence in another place, he adds.

Unger and co-investigators decided to assess barriers to cancer clinical trial participation because of the issue’s importance, he says.

“Patient participation in clinical trials is the backbone of clinical cancer research,” Unger explains.

“A great deal of attention and research has been paid to the reasons why patients don’t participate in trials,” he adds. “Although this research is important, it leaves the impression that patients themselves are the main barrier to trial participation, when, in fact, many structural and clinical barriers get in the way long before patients are offered the option of a trial.”

The study’s findings confirm this: “Nearly 56% of patients didn’t have a trial available to them at their institution, and nearly 22% were deemed ineligible for an available trial,” he says. “Together, these structural and clinical factors alone are the main reasons why more than three out of four cancer patients don’t participate in trials.”

Similar structural barriers likely affect clinical trial participation in noncancer clinical trials, he says.

“It’s very likely that similar patterns exist for clinical trials in other diseases, since the factors underlying structural barriers, such as the absence of a locally available trial, and clinical barriers — especially not meeting the trial inclusion criteria — are not specific to cancer,” Unger explains.

The solution to breaking down structural barriers is for research institutions to find better ways to connect patients to trials, he says. Strategies can include making trials available at many more sites or providing more sites with the necessary resources to participate.

“IRBs could also focus on whether exclusion criteria for trials are adequately justified by concerns about patient safety, and whether some criteria could be modified or removed to make trial participation more inclusive,” Unger says.

Another strategy would be to reimburse patients for the costs of participating in trials, which is vitally important if the goal is to reduce income disparities in clinical trial participation. The current reality is that patients with greater financial means are more likely to be able to travel far distances to receive care in a trial, he adds.

“Overall, we need better ways to both bring the trials to the patients or the patients to the trials,” Unger says.


1. Unger JM, Vaidya R, Hershman DL, et al. Systematic review and meta-analysis of the magnitude of structural, clinical, and physician and patient barriers to cancer clinical trial participation. J Natl Cancer Inst. 2019 Mar 1;111(3):245-255. doi: 10.1093/jnci/djy221.