Racial disparities in clinical trial enrollment among patients with advanced cancers in community practices.

124 Background: Clinical trials are essential for advancing cancer treatment, yet racial disparities in trial participation persist. This study examined trends in clinical trial enrollment in community oncology settings, focusing on racial differences. Methods: We retrospectively analyzed data from the Flatiron Health Research Database from adult patients with advanced cancers (melanoma, head/neck, breast, thoracic, GI, GU, GYN), treated in community oncology practices (2010–2024), and received care at a trial-available practice with documented cancer treatment. Clinical trial participation was defined as receipt of a clinical study drug. Minority groups (Asian, non-Hispanic Black NHB, and Hispanic) were compared to non-Hispanic White (NHW), using multilevel logistic regression, adjusting for patient- (demographics, clinical characteristics), provider- (clinical service, referral patterns), and practice-level (patient volume, staff volume, trial capacity, minority proportions, community socioeconomic status) factors. A robust sandwich variance estimator accounted for clustering within physicians and practices. Results: Among 205,743 patients treated by 1,664 physicians across 107 community practices, 10,869 (5.3%) received a clinical study drug: Asian (1.6%), NHW (68%), NHB (5.7%), and Hispanic (3.6%). Annual enrollment rates increased from 4.0% in 2011 to 6.9% in 2024. Compared to NHW, odds of trial participation were significantly lower among Hispanic (50% lower), Asian (49% lower), and NHB (43% lower) after adjusting for patient’s demographics and clinical characteristics (all p < 0.01). Further adjustment for provider- and practice-level factors reduced disparities, with NHB remaining 29% lower enrollment with statistical significance (Table). Sensitivity analysis confirmed the robustness of primary findings, with consistent associations across selective cohorts: 182,016 patients consistently cared for by trial-enrolling physicians, and a more restricted cohort of 121,922 patients from the 43 practices with the highest enrollment rates (top 40th percentile). Conclusions: Despite modest improvements in trial enrollment over time, racial disparities persist, with potential accentuation occurred in advanced cancer care, partly attributable to physician and practice influences. In addition, the continued disparity among NHB patients indicates that unmeasured factors beyond provider and practice factors may contribute to their lower enrollment. These findings underscore the need for targeted interventions to improve equitable access to innovative cancer therapies in community oncology settings. Primary Cohort aOR (95%CI) Minority groups/Adjusting factors Patient-level Patient-, physician-, & practice-level Asian 0.52 (0.32 – 0.83) 0.77 (0.59 – 1.0) NHB 0.57 (0.45 – 0.73) 0.71 (0.6 – 0.83) Hispanic 0.5 (0.31 – 0.81) 0.92 (0.77 – 1.11)