The ratio of women to men enrolled in oncology clinical trials still lags behind disease patterns in the real world, a new study has found.

Researchers led by Dr Reshma Jagsi from the University of Michigan Comprehensive Cancer Center in Ann Arbor, US reviewed 661 prospective clinical cancer studies, involving more than 1 million participants in total, that appeared in eight leading medical journals during 1986. The results were published in the 15 June issue of CANCER, a peer-reviewed journal of the American Cancer Society.

The review focused on studies of cancer types that are not gender-specific, such as colon cancer, oral cancers, lung cancer, brain tumours, haematologic cancers, head and neck cancers, and lymphomas. Published research was analysed according to factors such as the number of participants, the gender of the participants, the type of cancer and the funding source.

The ratio of women to men in the studies was expressed in two ways: the overall percentage of women in all of the studies and the average percentage of women from each study. As the researchers noted, the first method gave more weight to larger studies while the second gave each study equal weight.

With both analyses, though, the conclusion was the same: the representation of women in the studies was lower than expected, based on general population data for cancer incidence.

On average, women made up 38.8% of patients enrolled in the cancer studies. With each of the seven non-sex specific cancer types assessed, the majority of studies enrolled a lower proportion of women than those with that type of cancer in the general population, Dr Jagsi’s team reported. If haematologic cancers were excluded, a significantly lower proportion of women were enrolled compared with the real-life disease trend.

There was a small improvement in the ratios where government funding was involved. The proportion of women enrolled in cancer studies that relied on government funding was 41.3% versus 36.9% for studies supported by private funds. This may reflect not only government policies encouraging more balanced enrolment but also differences in review processes, grant size or research priorities, the authors suggested.

As Dr Jagsi et al pointed out, traditionally researchers were told to exclude vulnerable populations from clinical studies, including women of childbearing age. Among other barriers to participation identified by previous studies have been lack of information, fear, and perceived interference with personal responsibilities such as childcare.

“Women today are often stretched very thin trying to deal with the balance between their domestic responsibilities, their cancer diagnosis, and often a career as well,” Dr Jagsi commented. “They may be particularly likely to find clinical trials too burdensome. In that case, researchers should consider providing compensation to help with transportation or child care expenses.”

The studies reviewed by Dr Jagsi and colleagues were taken from the New England Journal of Medicine, the Journal of the American Medical Association, the Lancet, the Journal of Clinical Oncology, the Journal of the National Cancer Institute, Lancet Oncology, Clinical Cancer Research and CANCER.