Socioecological factors may mitigate racial, ethnic disparities in breast tumor biology

Key takeaways:

• Black, American Indian and Alaskan Native vs. white women had greater odds of tumors with high-risk recurrence scores.
• Black vs. white women living in urban areas had greater odds of high-risk recurrence scores.

Socioecological factors may explain the disproportionate impact of aggressive breast tumor phenotypes for racial and ethnic minority women, according to study results published in JAMA Network Open.

“Racial disparity in breast cancer mortality is attributed to socially determined factors, such as greater exposure to social and environmental risk factors and inequitable access to health care,” Ashwini Z. Parab, MS, from the department of pharmacy systems, outcomes and policy at the University of Illinois, and colleagues wrote. “Although studies have found that neighborhood disadvantage, inadequate insurance coverage and urban residence are associated with worse breast cancer outcomes, whether these social and environmental factors influence tumor biology among non-Hispanic Black women is not known.”

Parab and colleagues conducted a population-based, retrospective, observational cohort study that used the Surveillance, Epidemiology and End Results (SEER) Program Oncotype DX database to obtain data on the 21-gene recurrence score for 69,139 women (mean age, 57.7 years). All women were diagnosed with stage I to II estrogen receptor-positive breast cancer from 2007 to 2015. Researchers evaluated individual-level and area-level socioeconomic position and urban or rural residence as factors that may mediate racial and ethnic differences in estrogen receptor-positive breast tumors.

Primary outcome was the likelihood of a high-risk recurrence score of 26 or greater.

Overall, 74% of women were white, 9.1% were Hispanic, 8.7% were Asian and Pacific Islander, 7.8% were Black and 0.4% were American Indian and Alaskan Native. Of these, 17.5% of Black, 17.9% of American Indian and Alaskan Native, 14.5% of Asian and Pacific Islander, 13.8% of Hispanic and 13.7% of white women had tumors with a high-risk recurrence score.

Researchers observed a greater likelihood of high-risk recurrence scores among Black (OR = 1.33; 95% CI, 1.23-1.43) and American Indian and Alaskan Native (OR = 1.38; 95% CI, 1.01-1.86) women compared with white women. Hispanic and Pacific Islander women had no significant differences in the likelihood of high-risk recurrence scores compared with white women.

Black women living in urban areas had greater odds of high-risk recurrence scores compared with white women (OR = 1.35; 95% CI, 1.24-1.46). Researchers did not observe greater odds of high-risk recurrence scores for Black women living in rural areas compared with white women (OR = 1.05; 95% CI, 0.77-1.41).

In the mediation analysis, lack of insurance, county-level disadvantage and urban vs. rural residence accounted for 7% to 20% of racial and ethnic differences in high-risk recurrence score prevalence. Researchers noted that the contribution of these variables was only significant for Black women (P < .001).

“Future research should examine the possibility that ancestry-related genetic factors may act as effect modifiers,” the researchers wrote. “Additional research is needed with more comprehensive and nuanced measures of the social and environmental exposures that urban non-Hispanic Black and non-Hispanic American Indian and Alaskan Native women are subjected to.”