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TOPLINE:

A retrospective study validates the Oncotype 21-gene breast recurrence score as a predictive biomarker of adjuvant chemotherapy benefit in women with estrogen receptor (ER)-positive/human epidermal growth factor receptor 2 (HER2)-negative breast cancer by race and ethnicity.

METHODOLOGY:

• The Oncotype 21-gene breast recurrence score is a common biomarker used in the United States to help make treatment decisions for ER-positive, HER2-negative breast cancer patients without axillary lymph node metastases.
• The researchers aimed to verify the accuracy of the recurrence score in racial and ethnic minority groups that are not adequately represented, taking into account the potential variations in breast cancer death rates.
• This retrospective cohort study analyzed data from women aged 18 or older with stages I-II, axillary node-negative, and ER-positive breast cancer between 2004 and 2015.
• Of the 73,363 women included, 8.2% were Asian/Pacific Islander, 7.8% were non-Hispanic Black, 9.1% were Hispanic, and 74.9% were non-Hispanic White.
• The study evaluated the impact of the 21-gene breast recurrence score on breast cancer death, categorized by low-, intermediate-, and high-risk levels with a median follow-up of 56 months.

TAKEAWAY:

• Use of chemotherapy was significantly higher in non-Hispanic Black women (22.45%) than in Asian/Pacific Islander (20.87%), Hispanic (20.31%), and non-Hispanic White (19.13%) women (P < .0001).
• The risk for breast cancer deaths was significantly reduced with chemotherapy in non-Hispanic Black (hazard ratio [HR], 0.70), Hispanic (HR, 0.38), and non-Hispanic White women (HR, 0.75). These associations remained statistically significant in high-risk recurrence score categories.
• Chemotherapy use did not improve breast cancer mortality in Asian/Pacific Islander women overall (HR, 0.67; 95% CI, 0.42-1.07) or in any risk category.
• The exploratory subgroup analysis showed that among women aged 50 or younger with intermediate risk, the trendlines for the 7-year breast cancer death rate suggest a lower potential cutoff for recommending chemotherapy in non-Hispanic Black women than in non-Hispanic White women.

IN PRACTICE:

According to the authors, "this study clinically validated [recurrence score] as a predictive biomarker in non-Hispanic Black, Hispanic, and non-Hispanic White women," and prospective trials should be undertaken to confirm lower recurrence score cutoffs in non-Hispanic Black women aged 50 years and younger.

SOURCE:

This study, led by Hsiao-Ching Huang, MPH, PhD, from the University of Illinois College of Pharmacy, Chicago, Illinois, was published online on January 8, 2024, in the Journal of the National Comprehensive Cancer Network.

LIMITATIONS:

This study is limited by its retrospective design and potential unmeasured confounding variables. Data on adjuvant endocrine therapy use were lacking, and there was incomplete information on chemotherapy in the SEER registry. Also, the HER2 status for patients included before 2010 was unknown.

DISCLOSURES:

This work was supported by the AbbVie Fellowship in Pharmacovigilance and Patient Safety and the National Cancer Institute of the National Institutes of Health. Some authors reported receiving financial support outside this work.