Race may affect breast cancer outcomes among women with similar genetic recurrence scores
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SAN ANTONIO — Outcomes among women with breast cancer who have similar 21-gene recurrence scores may vary by race, according to study results presented at San Antonio Breast Cancer Symposium.
An analysis of patients with hormone receptor-positive, HER2-negative, lymph node-positive disease revealed worse outcomes among non-Hispanic Black women than non-Hispanic white, Asian or Hispanic women.
“Racial disparities in breast cancer outcomes continue to be a major health care challenge, with Black women more likely to die [of] the disease than non-Black women,” researcher Yara Abdou, MD, assistant professor at The University of North Carolina at Chapel Hill and Lineberger Comprehensive Cancer Center, said in a press release. “There is now wide-ranging evidence for differences in tumor biology contributing to this disparity. Understanding these differences will help us discover new opportunities for intervention that will ultimately reduce cancer health disparities.”
The RxPONDER trial assessed whether the 21-gene recurrence score could predict the benefit of adjuvant chemotherapy with endocrine therapy for patients with lymph-node positive, hormone receptor-positive, HER2-negative breast cancer.
The score — which ranges from 0 to 100 — measures expression of 21 genes in tumor tissue to predict breast cancer recurrence risk and therapy response. This can help guide treatment decisions for women with early breast cancer, Abdou said.
Abdou and colleagues evaluated RxPONDER trial outcomes with regard to race and ethnicity.
The analysis included 4,048 women (70% non-Hispanic white, 15.1% Hispanic, 8% Asian and 6.1% non-Hispanic Black) with hormone receptor-positive, HER2-negative disease who had one to three positive axillary lymph nodes. All women had recurrence scores of 25 or less, which suggests low or intermediate recurrence risk.
The 21-gene recurrence scores appeared similar across racial subgroups, with no significant differences in number of lymph nodes involved or tumor size.
However, results showed higher frequency of high-grade tumors among non-Hispanic Black (18%) and Hispanic (14%) women then non-Hispanic white (10%) and Asian (7%) women.
In analyses adjusted for recurrence score, treatment arm, menopausal status, age and disease grade, researchers reported a 5-year invasive DFS rate of 91.5% among white women. By comparison, they reported rates of 87.2% (HR = 1.37; 95% CI, 1-1.9) among non-Hispanic Black women, 91.4% (HR = 0.92; 95% CI, 0.71-1.19) among Hispanic women and 93.9% (HR = 0.67; 95% CI, 0.45-1) among Asian women.
However, further adjustment for BMI appeared to reduce the differences between groups, particularly between non-Hispanic Black and non-Hispanic white women (HR = 1.21; 95% CI, 0.81-1.82), and between Asian and non-Hispanic white women (HR = 0.74; 95% CI, 0.48-1.13).
As Healio previously reported, initial results from the RxPONDER trial — presented at San Antonio Breast Cancer Symposium in 2020 — showed premenopausal women with hormone receptor-positive, HER2-negative breast cancer, one to three positive lymph nodes and a recurrence score of 25 or less derived benefit from chemotherapy; however, postmenopausal women with the same disease characteristics and recurrence score did not.
In the current analysis, race did not predict the benefit of adding chemotherapy to endocrine therapy. Researchers observed no statistically significant difference in invasive DFS or distant RFS between non-Hispanic white and non-Hispanic Black women.
At 12 months, a comparable percentage of non-Hispanic Black and non-Hispanic white women remained on endocrine therapy (96% vs. 94.8%). This suggests differences in outcomes likely are not due to variations in treatment compliance within the first year, Abdou said.
Researchers acknowledged study limitations. The small numbers of patients in racial/ethnic minority cohorts in the RxPONDER trial limited the statistical power of some analyses, including those designed to assess associations between treatment outcomes and race/ethnicity. In addition, longer follow-up of endocrine therapy adherence is necessary to evaluate the effect of therapy compliance on outcomes by race, according to researchers.
“In accordance with previous studies, our results indicate racial disparities in breast cancer — particularly in [hormone receptor]-positive breast cancer,” Abdou said. “These differences were observed despite analyzing a carefully chosen and uniformly treated study population, suggesting that biological factors other than disparities in care may be contributing to inferior outcomes in racial minorities. Our findings also highlight the necessity for greater representation of racial and ethnic minorities in clinical trials.”