Sex differences appear to persist in recruitment to clinical trials for new therapeutics across common solid cancer types.
An analysis of lung, colon, thyroid, melanoma, kidney, and pancreas cancer drug trials between 2000 and 2020 found women comprised 40% of the participants overall.
“We observed significant differences between the enrollment of sexes across all trial phases and tumour types except thyroid,” the researchers said.
“Drug trials for colon and kidney cancer enrolled the least number of women, with 33% participation rates.”
The apparent inequities in the recruitment of female participants in trials was observed across trial sites in the US, Canada, China, the UK and Australia.
However there seemed to be some modest improvement in female participation rates in recent years.
“Comparing 2000 to 2010 with 2011 to 2020, we observed a marginal increase in female participation, from 40% to 42%, respectively (P < .001).”
The Research Letter, published in JAMA Oncology, said 30 years have passed since the National Institutes of Health (NIH) Revitalisation Act (1993) which encouraged NIH-funded investigators to include adequate numbers of women in clinical studies.
The analysis found NIH-funded trials enrolled a higher proportion of women (48%) compared with industry trials (41%) (P < 0.001).
The researchers, including haematologist-oncologist Associate Professor Vinay Prasad from the University of California, San Francisco, said regulatory initiatives to increase female participation in drug trials over the past two decades may be insufficient.
They said women represented 77% of newly diagnosed thyroid cancer cases worldwide in 2020 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.”
“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,” they said.