Clinical trial participation among adolescents and young adults diagnosed with cancer in the United States (2004-2021).

1560 Background: Adolescents and young adults (AYAs, 15-39 years) have low historical participation in cancer clinical trials (CTs) than pediatric patients, which limits access to novel therapies and slows progress in outcomes. Although cooperative-group networks and AYA-focused initiatives have improved accrual, enrollment remains uneven across care settings and patient subgroups, highlighting the need for contemporary population-level estimates of participation and its predictors. Methods: The National Cancer Database was utilized to identify AYAs diagnosed between 2004 and 2021 with one of the 20 cancer types associated with the highest mortality. Patients with confirmed malignant neoplasms, known vital status, and ≥6 months of follow-up were included. The final analytic cohort comprised 865,923 patients. The primary endpoint was documented CT participation (yes/no). Multivariable logistic regression was used to estimate adjusted odds ratio (aOR) of enrollment by diagnosis epoch, age group, sex, race/ethnicity, insurance status, area-level education and median income, residence, Charlson-Deyo comorbidity score, and receipt of surgery, radiation, and systemic therapy. Results: Overall, 2,621 patients (0.3%) were enrolled in a CT. Enrollment increased from 0.1% (2004–2009) to 0.2% (2010–2013), 0.3% (2014–2017), and 0.5% (2018–2021); compared with 2004–2009, enrollment was higher in 2018–2021 (aOR: 4.92, 95% CI: 4.34–5.60). Compared to those aged <24 years, the odds of enrollment were lower for ages 25–29 (aOR: 0.52, 95% CI 0.46–0.58), 30–34 (aOR: 0.45, 95% CI 0.41–0.51), and 35–39 (aOR: 0.46, 95% CI 0.41–0.50). Enrollment was lower among non-Hispanic Black (aOR: 0.84, 95% CI 0.74–0.96) and Hispanic patients (aOR: 0.79, 95% CI: 0.69–0.90) compared to non-Hispanic White patients. Compared with uninsured patients, enrollment was higher among those with private (aOR: 1.74, 95% CI 1.38–2.21) or government insurance (aOR: 1.60, 95% CI: 1.26–2.05), and was also higher in areas with greater education attainment (aOR: 1.14, 95% CI: 1.03–1.25) and individuals in the high median income group (aOR: 1.13, 95% CI: 1.02–1.25). Patients who had received radiation (aOR 1.56, 95% CI 1.44–1.70) or systemic therapy (aOR 3.59, 95% CI 3.23–4.01) were more likely to enroll. Conclusions: CT participation among AYAs was exceedingly low but has increased over time. Differences in enrollment by age, race/ethnicity, insurance, and area-level socioeconomic measures suggest persistent barriers to CT access and participation. These findings support expanding trial availability beyond high-resource settings, strengthening AYA-focused referral pathways and infrastructure, and implementing equity-centered strategies such as navigation, reduced trial burden, and financial/insurance support to improve representation and access to investigational therapies.