New national data on the occurrence of triple-negative breast cancer (TNBC) among different racial groups confirms that the disease is more common among Black women nationwide. A state-by-state analysis in the study, published online in JAMA Oncology, shows that these trends persist at the state level.
The analysis revealed that incidence rate ratios of TNBC were significantly higher among Black women, compared with White women, in all states with data on this population. Rates ranged from a low of 1.38 in Colorado to a high of 2.32 in Delaware.
The state-level disparities highlight gaps in physicians’ understanding of how social factors contribute to disparities in TNBC risk and the need “to develop effective preventative measures,” the study authors explain.
“We’ve realized for a long time that Black women have a higher incidence of TNBC. This is related to the genetic signature of the cancer. So that is not at all surprising,” said Arnold M. Baskies, MD, past chairman of the national board of directors of the American Cancer Society, Atlanta, who was not involved in the research. However, “the variance of TNBC among women from state to state is somewhat surprising.”
Existing research shows that TNBC is diagnosed more frequently among non-Hispanic Black women than among other populations in the United States, but it’s unclear whether these racial and ethnic disparities differ at the state level.
The authors identified 133,579 women with TNBC from the U.S. Cancer Statistics Public Use Research Database whose conditions were diagnosed from January 2015 through the end of December 2019. Most patients (64.5%) were White, 21.5% were Black, nearly 10% were Hispanic, 3.7% were Asian or Pacific Islander, and 0.6% were American Indian or Alaska Native. States with fewer than 30 cases were excluded, as was Nevada, owing to concerns regarding data quality. That left eight states for American Indian or Alaska Natives, 22 for Asian or Pacific Islanders, 35 for Hispanic women, 38 for Black women, and 50 for White women.
Overall, the incidence ratios of TNBC were highest among Black women (IR, 25.2 per 100,000), followed by White women (IR, 12.9 per 100,000), American Indian or Alaska Native women (IR, 11.2 per 100,000), Hispanic women (IR, 11.1 per 100,000 women), and Asian or Pacific Islander (IR, 9.0 per 100,000) women.
The authors also uncovered significant state-by-state variations in TNBC incidence by racial and ethnic groups. The lowest IR rates occurred among Asian or Pacific Islander women in Oregon and Pennsylvania – fewer than 7 per 100,000 women – and the highest occurred among Black women in Delaware, Missouri, Louisiana, and Mississippi – more than 29 per 100,000 women.
In the 38 states for which data on Black women were available, IR rates were significantly higher among Black women in all 38, compared with White women. The IR rates ranged from a low of 1.38 (IR, 17.4 per 100 000 women) in Colorado to a high of 2.32 (IR, 32.0 per 100 000 women) in Delaware.
While genetics play a role in TNBC risk, “the substantial geographic variation we found within each racial and ethnic group is highly suggestive that there are structural, environmental, and social factors at play in determining women’s risk of TNBC,” said lead study author Hyuna Sung, PhD, senior principal scientist and cancer epidemiologist at the American Cancer Society, Atlanta.
Existing evidence indicates that Black and White women living in socioeconomically disadvantaged neighborhoods are at higher risk of developing more aggressive subtypes of breast cancer, Dr. Sung said. Another factor, Dr. Sung and co-authors note, is breastfeeding. Across races, women who breastfeed have lower rates of TNBC.
Getting more definitive answers as to what causes differences in TNBC rates across states and what strategies can help reduce these disparities will be difficult and requires more research. “We really need to do a better job at researching and treating TNBC to improve health care equality for all women,” Dr. Baskies said. “The mortality rates from this cancer are high, and we rely heavily on surgery and toxic chemotherapy to treat it.”
Dr. Sung agreed, noting that “the observed state variation in TNBC rates merits further studies with risk factor data at multiple levels to better understand the associations of social exposures with the risk of TNBC.”
In states such as Louisiana and Mississippi, which are known to have a disproportionately higher burden of many types of cancers, “addressing barriers to access to preventive care and empowering public health efforts to promote a healthy living environment are the best policy prescription that could be deduced from our results,” Dr. Sung concluded.
Dr. Baskies is on the board of directors of Anixa Biosciences, which is currently conducting a clinical trial of a TNBC vaccine at the Cleveland Clinic. Dr. Sung has disclosed no relevant financial relationships.
A version of this article first appeared on Medscape.com.