Clinical trials are critical to developing new therapies and improving existing regimens for better efficacy and safety.1 Clinical trials can only be conducted if they enroll sufficient numbers of patients, and the more rapid the accrual, the sooner results can be collected and analyzed, and, ultimately, translated to the clinical setting. However, it has been estimated that almost 39% of trials terminated prematurely were due to lack of accrual.2 It is also estimated that just 8% of patients with cancer participate in clinical trials.2

Given the continued need for better therapies for patients with cancer, and the difficulty with enrolling patients, it is important to understand why participation rates have historically been low.

A meta-analysis of 13 studies (representing 8883 patients) conducted in the academic and community settings identified structural and clinical barriers as the primary causes of low levels of patient participation in clinical trials.1 In the analysis, 56% of patients were unable to participate in a clinical trial because there were none available for their cancer type or stage. Of the remaining patients, 22% did not meet eligibility criteria for the available trials and 15% who were eligible did not enroll. Ultimately, 8% of the patients represented across the 13 studies enrolled in clinical trials. Interestingly, enrollment was higher at academic institutions (16%) compared with the community setting (7%; P <.001), with no differences in eligibility and non-enrollment. There were fewer trials available at the community centers, although the result was not determined to be significant.

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Barriers to Clinical Trial Enrollment

There are multiple barriers that prevent clinical trial enrollment. The meta-analysis demonstrated that trial availability and eligibility criteria are major barriers.1 Other barriers include patient- or physician-related factors.

Patient-Related Barriers

Many barriers that patients experience, particularly those of underserved populations or racial or ethnic minorities, are barriers to access.3,4 Some of these factors are related to the clinical trial availability issue, as patients must find a cancer center in a geographic area that is a reasonable distance from their home — and one that is also associated with a reliable and affordable means of transportation.3 Other access barriers include the ability to take time away from work, finding child care, and having access to insurance.

Patient attitudes and beliefs can also be a barrier to clinical trial participation. Some patients may fear the idea of randomization or unknown potential toxicities associated with experimental therapy.3 One survey found that 12% of patients who were aware of clinical trials chose not to participate due to fear of receiving placebo, and 21% did not enroll because they thought a trial would not help them.5 Some patients do not enroll because they may already have a strong opinion about which treatment they want to receive.3