Black women more likely to develop distant metastases from breast cancer
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Black women appeared nearly six times more likely than white women to develop distant metastases after breast cancer diagnosis, according to study results presented during the virtual ASCO Annual Meeting.
The finding — which persisted after researchers accounted for disease stage and patient age — suggests racial disparities continue to exist in development of distant metastases independent from late-stage diagnosis, researchers concluded.
“We were surprised to find that the differences in distant metastases after diagnosis [among] Black women vs. white women were so large,” Julia Blanter, MD, internal medicine resident at Mount Sinai Hospital, told Healio. “We were also surprised to find that it largely still exists despite accounting for age and stage at diagnosis.”
Breast cancer incidence is lower among Black women than white women; however, Black women have a poorer prognosis regardless of disease subtype, according to study background.
“When compared [with] white women, Black women have far lower rates of breast cancer but still have the highest breast cancer death rate of all racial and ethnic groups,” Blanter said. “This characteristic has often been attributed to late stage at diagnosis.”
Blanter and colleagues aimed to assess differences in rates of distant metastases — the biggest driver of breast cancer mortality — among white vs. Black women with breast cancer treated in the Mount Sinai Health System.
They performed a follow-up analysis of 441 women (white, n = 340; Black, n = 101) initially recruited as part of an NIH-funded cross-sectional study conducted from 2013 to 2020. That study examined the link between breast cancer prognosis and insulin resistance among self-identified Black or white women.
In their follow-up analysis, Blanter and colleagues retrospectively analyzed electronic medical records between September 2020 and January 2021 to assess metastases not present at initial diagnosis. They recorded disease stage at diagnosis for all women.
Researchers defined distant metastases after diagnosis as evidence of metastases in any secondary organ, excluding lymph nodes, at any time after treatment initiation.
Median age was comparable between white and Black women (57.5 years vs. 55.9 years). A higher percentage of white women than Black women had stage I disease (83.5% vs. 58.4%), whereas a higher percentage of Black women had stage II (28.7% vs. 13.2%), stage III (9.9% vs. 2.9%) or stage IV (3% vs. 0.3%; P < .0001 for all).
Median follow-up for all women was 2.95 years (3.12 years for white vs. 2.51 years for Black; P = .017).
Eleven women developed distant metastases after diagnosis; these included four (1.2%) white women and seven (6.9%) Black women (P = .004).
Multivariate analyses that adjusted for stage at diagnosis, age and race showed Black women were nearly six times as likely to have distant metastases as white women (OR = 5.8; 95% CI, 1.3-25.2).
Additional research is necessary to better understand the source of existing disparities, Blanter said. Contributing factors could include surveillance, treatment differences or follow-up, she added.
“[Although] practices may not change based on these findings, we believe our study opened the door for many future projects — namely, finding the source of the continued existing disparity,” Blanter told Healio. “In our study, we did note that Black women had [significantly shorter median follow-up time].
“However, we were unable to account for those who may have transitioned to care outside of the Mount Sinai Health System or those with a recent diagnosis who may have just not followed up yet,” she added .”It would be beneficial to look at this more closely and see if there are true differences in follow-up time and if they contributing to the poorer outcomes.”
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Blanter J, et al. Abstract 1084. Presented at: ASCO Annual Meeting (virtual meeting); June 4-8, 2021.
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