Breast Cancer Studies Neglect Key Social Factors, Say Scientists
Studies of breast cancer do not take sufficient account of patients’ race, ethnicity, economic status, education level, health insurance coverage, and other social factors, a group of scientists argue.
The researchers, in a commentary in the journal Cancer Causes and Control, point to evidence that social factors help determine people’s vulnerability to cancer. They argue that these factors should be considered routinely in research on both breast cancer risk and treatment outcomes.
“We’ve been missing opportunities to understand and reduce disparities in breast cancer risk and outcomes,” says lead author Lorraine T. Dean, assistant professor of epidemiology at the Johns Hopkins University Bloomberg School of Public Health.
“Simply put,” Dean says, “not enough is being done to understand how race, income level, and other social factors tie into cancer susceptibility.”
A 2014 review of more than 20 years of National Cancer Institute clinical trials, the authors say, found that only about 20% of the randomised controlled studies reported results stratified by race or ethnicity.
“For many years, a commonly used questionnaire for assessing breast cancer risk was validated only for white women.”
A follow-up analysis of 57 breast cancer observational and randomised controlled trials published in 2016 found that, after excluding those in which the primary focus was disparities, fewer than 5% reported findings stratified by race or other socioeconomic factors.
Neglecting race, ethnicity, and other social factors in medical research can mean missing important drivers of bad outcomes, Dean and her coauthors argue. For example, a recent non-cancer study sorted mortality rates by race and socioeconomic status; that revealed that midlife mortality is increasing among US blue-collar whites even as it is declining for the population overall. Those findings drew attention to increases in suicides and substance-abuse deaths and led researchers to zero in on economic despair and social decay as likely causes.
“A lot of scientists don’t want to deal with race or socioeconomic position in their studies because they think those characteristics aren’t modifiable,” Dean says. “But they can actually help identify factors that are modifiable. You can’t change your genes, for example, but we still do genetic studies because they illuminate pathways we can change with medicines or other interventions.”
Black Women at Risk
Dean and colleagues point out that standard breast cancer risk assessment tools have not always considered race, even though there are significant racial disparities in the risks for certain types of breast cancer and in breast cancer mortality.
For many years, a commonly used questionnaire for assessing breast cancer risk (now known simply as the Breast Cancer Risk Assessment Tool) was validated only for white women. It tended to underestimate the risks of breast cancers for black women, who have lower rates of mammogram screening and higher rates of breast cancer at younger ages. That error may have kept many black women from participating in cancer-prevention trials of drugs such as tamoxifen.
“The model was revised in 2015 to take race into account, and now estimates black female eligibility for chemoprevention at nearly three times the rate of the original model,” Dean says.