Sizable state variations in racial, ethnic disparities for triple-negative breast cancer

A cohort study published in JAMA Oncology found substantial state variations in racial and ethnic disparities in triple-negative breast cancer incidence, with Black women in four states having the highest rates.

“Prior studies on state-level triple-negative breast cancer incidence were limited by lower geographical coverage, lack of consideration of race and ethnicity or exclusion of racial and ethnic minority groups other than Black and white populations,” Hyuna Sung, PhD, senior principal scientist and cancer epidemiologist in the surveillance and health equity science department at the American Cancer Society, and colleagues wrote. “Furthermore, none of these studies reported on state variations in racial and ethnic disparities in triple-negative breast cancer rates.”

Using population-based cancer registry data for all 133,579 U.S. women with triple-negative breast cancer diagnosed from 2015 to 2019, researchers evaluated state and race and ethnicity reported from medical records in the U.S. Cancer Statistics Public Use Research Database.

The primary outcomes were triple-negative breast cancer diagnoses, age-standardized incidence rates per 100,000 women, state-specific incidence rate ratios using rates for white women in each state as the reference for disparities, and state-specific incidence rate ratios using the race and ethnicity-specific national rate as the reference for disparities.

In total, 0.6% of women were American Indian or Alaska Native, 3.7% were Asian or Pacific Islander, 21.5% were Black, 9.7% were Hispanic and 64.5% were white. Triple-negative breast cancer incidence rates were highest among Black women (25.2 per 100,000 women), followed by white women (12.9 per 100,000 women), American Indian or Alaska Native women (11.2 per 100,000 women), Hispanic women (11.1 per 100,000 women) and Asian or Pacific Islander women (9 per 100,000 women).

Researchers observed substantial variation in racial and ethnic group-specific and state-specific rates ranging from less than 7 per 100,000 women among Asian or Pacific Islander women in Oregon and Pennsylvania to more than 29 per 100,000 women among Black women in Delaware, Missouri, Louisiana and Mississippi. Incidence rate ratios were statistically significantly higher in 38 states among Black women, ranging from 1.38 in Colorado to 2.32 in Delaware. Incidence rate ratios were lower in 22 states among Asian or Pacific Islander women, ranging from 0.5 in Oregon to 0.82 in New York. Incidence rate ratios were not different among Hispanic women in 22 states and American Indian or Alaska Native women in five states compared with white women.

Despite smaller state variations within each racial and ethnic population, these variations were still substantial, with incidence rate ratios varying from 0.72 in Utah to 1.18 in Iowa, 1.15 in Mississippi and 1.15 in West Virginia among white women.

“These findings suggest a role of social determinants of health in these disparities and may encourage public health practitioners to identify specific regions and racial and ethnic groups on which to focus risk-reducing efforts,” the researchers wrote. “More research, however, is needed to elucidate factors contributing to these variations and to develop effective triple-negative breast cancer preventive measures, which may ultimately reduce disparities in breast cancer outcomes and lower the burden of death from breast cancer.”