Inclusion of Women in Oncology Clinical Trials From 2000 to 2020

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In a study reported in a research letter in JAMA Oncology, Jenei et al found that women with cancer have been underrepresented in global oncology drug trials over the past 20 years, with underrepresentation persisting through the present in multiple cancer types.   

Study Details

The study involved a systematic search for drug trials in lung, colon, thyroid, kidney, and pancreatic cancers, as well as melanoma, registered on between 2000 and 2020. A total of 505 clinical trials including 182,416 patients met criteria for analysis.

Key Findings

Among the 182,416 participants, 73,103 (40%) were women and 109,313 (60%) were men.

According to clinical trial phase, percentages of women vs men enrolled were 48% vs 52% for phase I, 43% vs 57% for phase II, and 38% vs 62% for phase III (all P ≤ .001).

According to tumor type, percentages were: 41% vs 59% for lung cancer, 33% vs 67% for colon cancer, 42% vs 58% for melanoma, 33% vs 67% for kidney cancer, 47% vs 53% for pancreatic cancer (all P < .001), and 51% vs 49% for thyroid cancer (P = .50).

By region, percentages were 40% vs 60% in the United States, 39% vs 61% in Canada, 41% vs 56% in China, 39% vs 61% in the United Kingdom, and 39% vs 61% in Australia.

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The percentage of enrolled women vs men improved from 40% to 60% in 2000 to 2010 to 42% vs 58% in 2011 to 2020 (P < .001).

By funding source in the United States, percentages of women were higher in National Institutes of Health–funded trails vs industry-funded trials (48% vs 41%, P < .001).

According to 2020 data from the International Agency for Research on Cancer, compared with incidence of new cases of cancer, women were underrepresented in trials in colon cancer, thyroid cancer, melanoma, and kidney cancer, but not in trials of lung cancer or pancreatic cancer. 

The investigators stated: “It is essential that women be enrolled in clinical trials in numbers that, at least, mirror the distribution of the disease in the population so that potential biological differences can be understood. Our analysis, although limited to six tumor types, suggests that sex differences persist in clinical trials. In 2020, women represented 77% of newly diagnosed thyroid cancer cases worldwide yet comprised only 51% of participants in trials investigating thyroid drugs. Similarly, women represented 48% of global colon cancer cases yet accounted for only 33% of trial participants for colon cancer therapeutics… Our analysis, although limited to sponsor- and manufacturer-disclosed information, demonstrates that persistent inequities remain in the recruitment of female participants in trials investigating new therapeutics for certain tumor types in oncology.”

Kristina Jenei, BSN, MSc, of the School of Population and Public Health, University of British Columbia, Vancouver, is the corresponding author for the JAMA Oncology article.

Disclosure: For full disclosures of the study authors, visit

The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.