Non-Hispanic Black patients with lymph node–positive, hormone receptor (HR)–positive/HER2-negative breast cancer experienced worse outcomes compared with the outcomes of non-Hispanic White, Asian, and Hispanic patients—despite similar 21-gene recurrence scores—according to new findings presented by Abdou et al at the San Antonio Breast Cancer Symposium (SABCS) 2022 (Abstract GS1-01).

Background

“Racial disparities in breast cancer outcomes continue to be a major health-care challenge, with Black [patients] more likely to die from the disease than non-Black [patients],” said study author Yara Abdou, MD, Assistant Professor of Hematology and Oncology in the Department of Medicine and an oncologist at the Lineberger Comprehensive Cancer Center at the University of North Carolina at Chapel Hill. “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.”

Research Methods and Results

Dr. Abdou and her colleagues analyzed the clinical outcomes with respect to race and ethnicity in the RxPONDER clinical trial—which aimed to assess the value of the 21-gene recurrence score in patients with lymph node–positive, hormone receptor–positive/HER2-negative breast cancer, and the benefit of adjuvant chemotherapy in these patients.

The researchers explained that the 21-gene recurrence score—the genomic test measuring the expression level of a group of 21 genes in the tumor tissue on a scale of 0 to 100 to predict the risk of breast cancer recurrence and the response to therapy—is an important tool to guide treatment decisions among patients with early-stage breast cancer.

The study included 4,048 patients who had hormone receptor–positive/HER2-negative breast cancer and one to three positive axillary lymph nodes, as well as 21-gene recurrence scores of 25 or lower (intermediate or low risk). The participants who were involved in the study identified as Non-Hispanic White (70% of participants), non-Hispanic Black (6.1%), Hispanic (15.1%), and Asian (8%).

The researchers found that the 21-gene recurrence scores were similar across all racial subgroups, and that there were no significant differences in tumor size and in the number of lymph nodes involved. However, non-Hispanic Black and Hispanic patients had a higher frequency of high-grade tumors—at 17.7% and 14.1%, respectively—than that of non-Hispanic White and Asian patients at 10.2% and 6.5%, respectively.

The 5-year invasive disease–free survival rate was also lower for non-Hispanic Black patients (87.2%) compared with the rate for Asian patients (93.9%), non-Hispanic White patients (91.5%), and Hispanic patients (91.4%). After adjusting for age, menopausal status, grade, treatment arm, and recurrence score, non-Hispanic Black patients had a 37% higher risk of invasive cancer than non-Hispanic White patients. Additionally, non-Hispanic Black patients had a lower distant relapse–free survival than that of non-Hispanic White patients.

According to the 2020 RxPONDER trial results, premenopausal patients with hormone receptor–positive/HER2-negative breast cancer and one to three positive lymph nodes, as well as 21-gene recurrence scores of 25 or lower benefited from the use of chemotherapy—while postmenopausal patients did not. In this new analysis by race, the researchers found that race did not predict the relative benefit of adding chemotherapy to endocrine therapy, as the clinical outcome by treatment arm was not significantly different between non-Hispanic Black and non-Hispanic White patients for invasive disease–free survival and distant relapse–free survival.

After 12 months of follow-up, the researchers discovered that 96% of non-Hispanic Black patients were still on endocrine therapy compared with 94.8% of non-Hispanic White patients.

Conclusions

“These data suggest that the differences in long-term outcomes are not likely attributable to lack of treatment compliance among [non-Hispanic] Black [patients] within the first year; however, longer follow-up is needed to confirm this finding,” underscored Dr. Abdou.

“In accordance with previous studies, our results indicate racial disparities in breast cancer, particularly in [hormone receptor]–positive breast cancer. 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,” Dr. Abdou continued, indicating that “Our findings also highlight the necessity for greater representation of racial and ethnic minorities in clinical trials.”

The researchers concluded that longer follow-up of endocrine therapy adherence may be needed to assess the impact of therapy compliance on different outcomes by race—and that “there remains an important need for novel approaches to improve clinical outcomes particularly for [non-Hispanic] Black [patients].”

Disclosure: The research in this study was funded by National Institutes of Health and National Cancer Institute grants, Susan G. Komen for the Cure research program, Hope Foundation for Cancer Research, Breast Cancer Research Foundation, and Exact Sciences Corporation.