As doctors become more familiar with the different types of breast cancer—those where the tumors are driven by hormones or certain genetic mutations, for example—they've learned that women with different racial and ethnic backgrounds may have different risks of developing certain types of cancer.
Biology and genetics certainly play a role, but in the latest study published in Cancer Epidemiology, Biomarkers & Prevention, scientists describe some other factors that are just as important.
Recent studies show that African-American women tend to develop a particularly aggressive form of breast cancer called triple negative, which got its name because the tumors don’t recognize hormones like estrogen or progesterone or the protein HER2, all of which trigger abnormal growth but can be thwarted with current drugs. These women also tend to be at later stages of the disease when they are diagnosed, leaving them few, if any, options for treatment.
In the latest study, the researchers, led by Lu Chen from the division of public health sciences at Fred Hutchinson Cancer Research Center, and her colleagues report that not only are African-American women more likely to be diagnosed at later stages with the most aggressive form of the disease, but they are also more likely than white women to be diagnosed at later stages for all types of breast cancer. Among the 102,064 women across a broad range of social, economic and cultural strata from 18 different cancer centers who were diagnosed with breast cancer, African-American, Hispanic, Asian and American Indian women showed 20% to 60% higher rates of diagnosis with stage 2 to stage 4 breast cancers of any type compared to Caucasian women. The risk was highest among African-American women, who had a 40% to 70% greater risk of being diagnosed with stage 4, the most advanced, of any type of breast cancer, compared to white women.
That strongly suggests that while biology and genes contribute to a heightened risk of cancer, social and cultural factors such as lower incomes may be driving the worse outcomes experienced by these women when they are diagnosed. Studies have shown that African-American, Hispanic and Native American women tend to have less access to screening mammograms, for example. And in Chen’s study, she found that they are also less likely to get the recommended treatment for their disease. Many received surgery to remove tumors but did not receive the follow-up radiation to lower the risk of spread and recurrent growths.
“There are a lot of reasons why these women have a higher incidence of particular subtypes of breast cancer that may have something to do with genetics and biological factors,” says Chen. “But being diagnosed at a later stage and not receiving treatment—these disparities we think have more to do with social, cultural and economic factors.”
That may result from a combination of factors involving both the doctor and patient. In some cases, especially in lower income neighborhoods, doctors may not fully explain the reasoning behind or the need for treatment and what it’s supposed to accomplish. Cultural barriers including language and differing philosophical beliefs about therapies may also contribute to the lower rates of complete treatment among minority populations. “We don’t know if they don’t get the recommendations about treatment [from their doctors] or if they couldn’t afford the treatment, or something else,” she says.
Knowing that non-white women overall tend to be diagnosed at later stages for all types of breast cancer, and that they receive sub-optimal treatment, could help to change that potentially life-threatening pattern. Treatment decisions are increasingly dictated by the subtype of cancer that’s in the breast: whether it's dotted with hormone receptors, and if so, which type. Addressing the non-medical barriers that are preventing minority women from taking full advantage of these therapies in a timely way could potentially save more lives, says Chen.