Female participation in U.S. oncology clinical trials registered on ClinicalTrials.gov from 2008 to 2020.

85 Background: Females are thought to be underrepresented in clinical trials, which may lead to care disparities. We characterized female enrollment trends in U.S. oncology trials registered on ClinicalTrials.gov and identified features associated with accurate representation. Methods: We employed a cross-sectional study design with descriptive, logistic regression, and cox regression analyses. We downloaded 270,172 studies registered on the Aggregate Analysis of the ClinicalTrials.gov database from October 1, 2008 to March 9, 2020, excluding non-interventional and reproductive organ specific trials. We then applied cancer/oncology specific Medical Subject Heading terms and manually reviewed the remaining 27,521 trials for true oncology content. Prevalence-corrected estimates for female participation were calculated as the percentage of females among trial participants divided by the percentage of females in the disease population per U.S. Surveillance, Epidemiology, and End Results Program (SEER) data (participation to prevalence ratio [PPR]), with a range between 0.8 and 1.2 reflecting accurate female representation in the trial. Results: Of 26,894 trials meeting eligibility criteria, 9,059 trials were completed in the U.S., 2,499 trials reported completed study status, and only 1,256 trials reported sex. Among 1,256 oncology trials and 229,056 participants, overall female representation was 46.9% (95% CI, 45.4-48.4%). 43% of trials were industry funded, 29% academic, and 28% U.S. government. Females were underrepresented compared to their disease burden in anal canal (PPR 0.21), thyroid (PPR 0.57), stomach (PPR 0.68), kidney (PPR 0.77), and bone (PPR 0.79) cancer trials. They were accurately represented in head and neck (PPR 0.80), lung (PPR 0.84), bladder (PPR 0.85), skin (PPR 0.88), pancreas (PPR 0.88), colon (PPR 0.90), hematologic (PPR 0.91), liver (PPR 1.01), CNS (PPR 1.03), soft tissue (PPR 1.05), and esophagus (PPR 1.05) cancer trials. Accurate representation was significantly associated with industry funding and pancreas cancer trial focus, but not associated with trial type (medical, surgical, radiation, other invasive, other) (Table). Conclusions: Females are underrepresented compared to their disease burden in many solid tumor clinical trials. Stakeholders can look to industry funded and pancreas cancer trials as models of improvement, but must increase female representation in clinical trials to improve cancer care. [Table: see text]