BackgroundIncluding racial and ethnic minorities in clinical trials is essential for advancing health equity. Despite progress, trials often do not mirror patient population demographics.MethodsThe National Library of Medicine's Clinical Trials database was queried for phase III trials of lung, colorectal, breast, and prostate cancers. A reference population was identified from the Surveillance, Epidemiology, and End Result (SEER) database, covering 48% of the US population.ResultsAmong 181 trials, race and ethnicity data were included in 86.7% and 60.2% of trials, respectively, with improving reporting over time. Participants were predominantly White (76.3%), followed by Asian/Pacific Islander (14.1%), Black/African American (4.5%), and American Indian/Alaska Native (0.6%). Hispanic/Latino constituted 6.4% of participants. The proportion of non-White groups increased from 19.4% in trials started before 2011 to 26.2% after 2015. Compared with SEER data, the percentages were lower for Asian/Pacific Islander across all cancers, Black/African American in breast and prostate cancers, American Indian or Alaska Native in colorectal, breast, and prostate cancers in US solely trials.ConclusionsReporting and enrollment of racial and ethnic minorities in trials remain inadequate but improving. To enhance diversity, real-world data are warranted to identify recruitment goals by better assessing the geographic distribution within the patient population.