"When Offered to Participate": A Systematic Review and Meta-Analysis of Patient Agreement to Participate in Cancer Clinical Trials

Abstract

Background: Patient participation in clinical trials is vital for knowledge advancement and outcomes improvement. Few adult cancer patients participate in trials. Although patient.

decision-making about trial participation has been frequently examined, the participation rate for patients actually offered a trial is unknown.

Methods: A systematic review and meta-analysis using 3 major search engines was undertaken. We identified studies from January 1, 2000, to January 1, 2020, that examined clinical trial participation in the United States. Studies must have specified the numbers of patients offered a trial and the number enrolled. A random effects model of proportions was used. All statistical tests were 2-sided.

Results: We identified 35 studies (30 about treatment trials and 5 about cancer control trials) among which 9759 patients were offered trial participation. Overall, 55.0% (95% confidence interval [CI] = 49.4% to 60.5%) of patients agreed to enroll. Participation rates did not differ between treatment (55.0%, 95% CI = 48.9% to 60.9%) and cancer control trials (55.3%, 95% CI = 38.9% to 71.1%; P = .98). Black patients participated at similar rates (58.4%, 95% CI = 46.8% to 69.7%) compared with White patients (55.1%, 95% CI = 44.3% to 65.6%; P = .88). The main reasons for nonparticipation were treatment choice or lack of interest.

Conclusions: More than half of all cancer patients offered a clinical trial do participate. These findings upend several conventional beliefs about cancer clinical trial participation, including that Black patients are less likely to agree to participate and that patient decision-making is the primary barrier to participation. Policies and interventions to improve clinical trial participation should focus more on modifiable systemic structural and clinical barriers, such as improving access to available trials and broadening eligibility criteria.

Figure 1.

Selection of studies included in the analysis

Figure 2.

Forest plots of the study-level and summary estimates for each domain. The boxes show the study-level estimate and the 95% confidence intervals. The overall effect is a summary measure for all trials combined. This is indicated by the dashed vertical line. CI = confidence interval.

Figure 3.

Sensitivity analysis results for the “leave one out” method. Under this approach, each of the individual studies is left out of the calculation of the meta-analytic rate one at a time, and the rate is recalculated using the random-effects approach. Each panel shows the absolute percentage increase or decrease in the overall estimated rate for all trials, for treatment trials, and for cancer control trials, respectively. The primary estimates are also shown. The results are ordered in descending order from largest absolute positive percentage change to largest absolute negative percentage change.

Figure 4.

Study specific estimates over time