Dividing breast cancer cell
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Investigators at the University of Illinois Chicago (UIC) have developed new data that show a commonly ordered breast cancer biomarker test to help clinicians decide whether breast cancer patients should receive chemotherapy may be making bad recommendations for some Black women who take the test.

The test, The Oncotype 21-gene breast recurrence score (RS) is the most commonly ordered multigene breast cancer biomarker in the United States. The NCCN Clinical Practice Guidelines in Oncology (NCCN Guidelines) for Breast Cancer base its recommendations on the RS for patients with estrogen receptor (ER)–positive, HER2-negative tumors that do not have axillary lymph node metastases. The test was developed as a predictive biomarker to identify which patients are likely to derive benefit from adjuvant chemotherapy, versus those who won’t.

The investigators for the new study, published in the Journal of the National Comprehensive Cancer Network, conducted a statistical analysis of 70,000 records that included both test results and death records of women with early-stage estrogen receptor-positive (ER-positive) breast cancer. Analysis of the data indicated that the test may underestimate the benefit of chemotherapy by ranking some patients—especially younger patients—as unlikely to benefit from chemotherapy, when they may have benefitted.

Based on this initial finding the researchers did further analysis on the cutoff point for the breast cancer biomarker test and found that it could still be useful for Black women if the cutoff point were lowered. While more research is needed before making this recommendation in the NCCN Guidelines, senior author, Kent Hoskins, MD, a professor of oncology at UIC, notes that “the research shows that it may be inappropriate for doctors to use exact cutoffs and tests regardless of race or ethnicity because there are underlying differences in biology.”

The vast majority of the patients with this form of breast cancer receive estrogen blocking medications, regardless of whether they also receive chemotherapy. The investigator speculate that the cause of the chemotherapy treatment gap is due to the fact that the breast cancer tumors of Black women are less likely to respond to these estrogen-blocking treatments. Because of this, outcomes for Black women are improved more from chemotherapy than they are for those women who benefit from the estrogen-blocking pills alone.

The new findings are one component of a braoder effort by UIC researchers to better understand the disparity of treatment outcomes for Black women with ER-positive breast cancer tumors. Previous research by the team has shown that Black women also have harder-to-treat triple-negative breast cancer (TNBC) and that they are more likely to get TNBC than their White counterparts. While Black women aren’t more likely to die from TNBC, they do have higher death rates in ER-positive breast cancer, a more common form of the disease.

The UIC team will continue their research with the intent to better understand and validate these early findings “If confirmed, the RS cutoff for recommending adjuvant chemotherapy for young non-Hispanic Black women with ER-positive, axillary node–negative breast cancer may need to be lower than for other women,” the researchers wrote. “This study also underscores the need to account for the racial and ethnic diversity of the target population in the development and validation of cancer biomarkers.”

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