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Black women with axillary node-negative breast cancer had a higher risk of death compared to white women, despite similar 21-gene recurrence scores, a cohort study found.

Among more than 85,000 women with estrogen receptor (ER)-positive breast cancer in the Surveillance, Epidemiology, and End Results (SEER) Oncotype DX 2004-2015 database, Black women were more likely to have a high-risk recurrence score (25 or above) compared with non-Hispanic white women (17.7% vs 13.7%, P<0.001), reported Kent Hoskins, MD, of the University of Illinois, and colleagues in .

In multivariable analysis of patients with node-negative disease, breast cancer-specific mortality was not only higher among Black women overall (HR 1.72, 95% CI 1.29-2.31), but also within different Oncotype DX risk levels:

• 0 to 10: HR 2.54 (95% CI 1.44-4.50)
• 11 to 25: HR 1.64 (95% CI 1.23-2.18)
• >25: HR 1.48 (95% CI 1.10-1.98)

"This study suggests that Black women in the U.S. with ER-positive, ERBB2-negative, axillary lymph node-negative breast cancer are more likely to have a high-risk RS [recurrence score] and to experience breast cancer-specific mortality compared with non-Hispanic white women within the same risk group," Hoskins and co-authors wrote. "In addition, the RS provides less prognostic information for Black women."

Accuracy of the 21-gene recurrence score was significantly worse for Black women (C index 0.656, 95% CI 0.592-0.720) versus non-Hispanic white women (C index 0.700, 95% CI 0.677-0.722; P=0.002).

"The findings suggest that Black women disproportionately develop aggressive ER-positive tumors and that the Oncotype DX Breast Recurrence Score test incompletely defines prognosis in these women," the authors wrote. "Genomic prognostic assays may require recalibration for racial/ethnic minority groups."

The retrospective analysis looked at 86,033 women (mean age 57.6 years) in the SEER Oncotype DX 2004-2015 registry who were diagnosed with stage I-III ER-positive breast cancer from 2004 to 2015. Three-quarters of the cohort were non-Hispanic white, 7.8% were non-Hispanic Black, 9.2% were Hispanic, 8% were Asian/Pacific Islander, and 0.4% of the women were American Indian/Alaska Native.

In an , Joseph Sparano, MD, of Albert Einstein College of Medicine in New York City, and Otis Brawley, MD, of Johns Hopkins School of Medicine in Baltimore, said the findings "confirm in a large population-based cohort reflecting real-world practice what has been previously reported for Black women participating in the , in other more limited , and also in a cohort derived from the National Cancer Database reflecting practice in accredited cancer centers."

But Sparano and Brawley pointed to limitations in the current study, including the short follow-up time (less than 5 years), no data on endocrine therapy adherence, missing information on social determinants of health, as well as a lack of information on the effect of patients' ethnicity.

"Reassuringly, however, to our knowledge there is no evidence from any study that the principal conclusions derived from TAILORx regarding use of the 21-gene RS to guide chemotherapy does not also hold true for racial and ethnic minorities," the editorialists wrote.

"In addition, although the findings have substantial importance at the population level, the effect for individual patients for whom the RS is being used to provide prognostic information is limited," they continued. "For example, the crude breast cancer mortality rate for non-Hispanic Black women was only about 1% for those with node-negative disease and a RS of 0 to 25 treated mainly with endocrine therapy alone ... although this likely underestimates the ultimate cancer mortality burden due to the limited follow-up."

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