Under-representation of women in high-impact published clinical cancer research
Reshma Jagsi, MD, DPhil 1 *, Amy R. Motomura, BSE 1, Sudha Amarnath, BS 2, Aleksandra Jankovic, MS 3, Nathan Sheets, BS 2, Peter A. Ubel, MD 3
1Department of Radiation Oncology, University of Michigan, Ann Arbor, Michigan
2University of Michigan Medical School, Ann Arbor, Michigan
3Center for Behavioral and Decision Sciences in Medicine, Department of Internal Medicine, Division of General Medicine, University of Michigan, Ann Arbor, Michigan
email: Reshma Jagsi (rjagsi@med.umich.edu)
*Correspondence to Reshma Jagsi, Department of Radiation Oncology, University of Michigan, UHB2C490, SPC 5010, 1500 East Medical Center Drive, Ann Arbor, MI 48109-5010
Presented in preliminary form at the American Society of Clinical Oncology 44th Annual Meeting, Chicago, Illinois, May 30-June 3, 2008.
Fax: (734) 763-7370
BACKGROUND.
Adequate representation of women in research has been deemed essential.
METHODS.
Cancer research published in 8 journals in 2006 was reviewed. The percentage of women among study participants was compared with the proportion expected from population-based estimates of sex-specific cancer incidence, using binomial tests. Differences were assessed in sex distribution of participants by funding source, author sex, and focus of research with the Student t test, and in a linear regression model controlling for cancer type.
RESULTS.
A total of 1534 cancer research articles were identified, of which 661 (representing 1,096,098 participants) were prospective clinical studies and were analyzed further. For all 7 non-sex-specific cancer types assessed, the majority of studies analyzed included a lower proportion of women than the proportion of women among patients having cancer of that type in the general population. Among studies focusing on cancer treatment, women constituted a significantly lower overall proportion of the participants in the analyzed studies than expected for 6 of 7 non-sex-specific cancer types (P < .001). Among non-sex-specific studies, the mean percentage of participants who were women was 38.8%. Non-sex-specific studies reporting government funding had a higher percentage of female participants (mean 41.3% vs 36.9%; P = .005). In a regression model controlling for cancer type, lack of government funding (P = .03) and focus on cancer treatment (P = .03) were found to be independent significant predictors of a lower percentage of female participants.
CONCLUSIONS.
Women were under-represented as participants in recently published, high-impact studie
From the full text of the study:
In 2001, the Institute of Medicine issued a report emphasizing that sex was an important basic human variable that should be considered when designing and analyzing studies in all areas and at all levels of biomedical and health-related research.[1] Indeed, sex may be a predictor not only of the incidence of disease, but also of the utility of diagnostic tests, preventive interventions, prognostic markers, and therapeutics. Not only may biologic differences between the sexes be important but also social and cultural influences based on sex, including gender differences in the approach of men and women with regard to their physicians and their own health, and how they communicate their health concerns.[2] The National Institutes of Health (NIH) has similarly recognized the critical role of sex in medicine; its Revitalization Act of 1993 explicitly articulated the importance of including women in each clinical research project and noted that clinical trials should enroll adequate numbers of female participants for performing valid subanalyses of the effect of trial variables on women alone.[3]
Fifteen years after the enactment of the NIH policy, however, it is still unclear whether women are adequately represented as subjects of clinical research. Whereas some analyses have suggested that women are adequately represented, others have suggested otherwise. For example, a study of federally funded randomized trials reported in 9 medical journals in 2004 found that women constituted only 37% of participants in non-sex-specific studies and 24% of participants in drug trials.[4]
Several previous studies have considered participation in cancer research specifically and also yielded mixed results. A study analyzing enrollment in Southwest Oncology Group trials from 1993 to 1996 revealed significant disparities between the proportion of women among enrolled trial participants and the proportion of women among the general population of US cancer patients for 3 of 11 cancer types they examined.[5] Another study of participation in cooperative group trials in 2000 through 2002 found that women were significantly less likely than men to enroll in trials for colorectal cancer (odds ratio, 1.30) and lung cancer (odds ratio, 1.23).[6] Yet, a different study of accrual to cooperative group studies found that overall, women did not accrue at lower rates and in fact, between the ages of 40 and 69 years, accrued at even higher rates than men. However, this finding was driven largely by participation in breast and gynecologic cancer studies; when studies were limited to non-sex-specific cancers, fewer women accrued than men.[7]
Despite the compelling nature of these findings, the researchers who conducted these studies have themselves acknowledged that their results may not be representative because their studies focused exclusively on cooperative group trial participation. Indeed, whereas cooperative group trials are funded by government sources, studies funded by industry or private philanthropy may be less sensitive to the need to enroll and analyze female patients than federally funded studies subject to the mandates of the NIH. Furthermore, patterns of enrollment in trials studying the impact of treatments may differ from enrollment in studies seeking to examine mechanisms of cancer causation and prevention. Therefore, further investigation is warranted to define better the representation of women as subjects in the full range of high-impact, clinical cancer research published today. This is particularly important in light of changes in political priorities that have made the competition for scarce federal research funds increasingly intense, potentially fueling an even greater reliance on private support. Indeed, although several other studies have also examined women’s representation among research participants, they too have generally focused on federally funded clinical trials[8-12] or have been limited in other ways, such as focusing on studies published in only 1 journal.[13] These studies have primarily focused on quantifying the representation of women rather than analyzing the role of various factors, such as funding source, in influencing their representation. The rare exceptions are dated.[14] Therefore, in this study, we sought both to update and build upon this previous work.
In this study, we attempted to quantify the representation of women as subjects in clinical cancer research studies, including not only trials but also prospective cohort studies, that result in high-impact publications. In addition, we assessed whether studies funded privately are as likely to include female participants as those with federal funding.
