Enrollment Patterns and Site-Level Predictors of Black Participant Recruitment to a Multisite Randomized Cancer...

Lack of race- and age-diversity in clinical trials adversely affects generalizability of trial results and equity of trial access. Research on barriers to representative accrual has focused on patient-level factors. We aimed to define site-level factors affecting the diversity of accrual to a multicenter clinical trial.

Alliance 191901 (GETSET) is a national randomized controlled trial testing interventions to promote breast cancer endocrine therapy adherence, which oversamples Black women and those under age 50 years at 30% thresholds. A secondary study objective is to examine site-level factors associated with accrual of Black and younger participants. At 50% accrual to the parent study, we performed prespecified analyses of association between site characteristics (region, neighborhood racial composition, Alliance membership type, number of recent accruals to cooperative research group trials) and the proportion of Black patients and younger patients accrued. We also examined trajectories of accrual over time for race- and age-specified subgroups.

The analysis included 124 sites. Among 590 participants, 9.7% were Black, and 22.4% were age <50 years. Neither site type nor historical accrual volume was associated with Black participant recruitment. Southern sites recruited higher proportions of Black participants (19.0% v 7.3% for West, P < .001). Neighborhood racial composition was positively associated with recruitment of Black participants (16.2% at sites from highest Black composition v 1.4% in lowest, P < .01). Recruitment trajectories of Black participants were slower than target rates, whereas those among non-Black participants were faster.

Neighborhood composition and geographic region were predictors of proportions of Black participants accrued to A191901 sites, but site type and historical accrual volume were not. When trials must limit site selection, identifying sites based on neighborhood composition and geography may be an appropriate tool for increasing trial diversity.