Representation of women in clinical trials supporting FDA-approval of contemporary cancer therapies

Abstract

Contemporary anticancer therapies frequently have different efficacy and side effects in men and women. Yet, whether women are well-represented in pivotal trials supporting contemporary anticancer drugs is unknown. Leveraging the Drugs@FDA database, clinicaltrials.gov, MEDLINE, and publicly available FDA-drug-reviews, we identified all pivotal (phase II and III) non-sex specific trials supporting FDA-approval of anticancer drugs (1998–2018). Observed-enrollment-rates were compared to expected-population-rates derived from concurrent US-National-Cancer-Institute's Surveillance-Epidemiology-and-End-Results (SEER) reported rates and US-Census databases. Primary outcome was the proportional representation of women across trials, evaluated by a participation-to-prevalence ratio (PPR), according to cancer type. Secondary outcome was the report of any sex-specific analysis of efficacy and/or safety, irrespective of treatment-arm. Overall, there were 148 trials, enrolling 60,216 participants (60.5 ± 4.0 years, 40.7% female, 79.1% biologic, targeted, or immune-based therapies) evaluating 99 drugs. Sex was reported in 146 (98.6%) trials, wherein 40.7% (24,538) were women, compared to 59.3% (35,678) men (p < .01). Altogether, women were under-represented in 66.9% trials compared to the proportional incidence of cancers by respective disease type; weight-average PPR of 0.91 (relative difference: -9.1%, p < .01). Women were most under-represented in gastric (PPR = 0.63), liver (PPR = 0.71), and lung (PPR = .81) cancer trials. Sex-based safety data was reported in 4.0% trials. There was no association between adequate female enrollment and drug efficacy (HR: 0.616 vs. 0.613, p = .96). Over time, there was no difference in the percentage of women recruited into clinical trials. Among pivotal clinical trials supporting contemporary FDA-approved cancer drugs, women were frequently under-represented and sex-specific-efficacy and safety-outcomes were commonly not reported.