Research led by the University Illinois Chicago shows a common genetic test, used by clinicians to help decide on treatment for women with estrogen receptor (ER) positive breast cancer, is less accurate in Black women.
The Oncotype DX 21-gene test creates a recurrence score that is designed to show which tumors are more aggressive and therefore good candidates for chemotherapy treatment. It’s the most ordered genetic test to assess breast cancer in the U.S. and the NCCN Clinical Practice Guidelines in Oncology recommend using the test to guide treatment in patients with ER-positive, HER2-negative tumors without axillary lymph node metastases.
The results of this study, published in the Journal of the National Comprehensive Cancer Network, show that the test may underestimate chemotherapy benefits for Black women with this kind of cancer, particularly those in younger age groups.
“This raises an important question regarding whether the 21-gene recurrence score has been adequately validated as a predictive biomarker in racial and ethnic minority patients,” write lead author Kent Hoskins, a professor of oncology at the University of Illinois Chicago, and colleagues.
“Fewer than 10% of participants in the validation studies of the recurrence score were non-Hispanic Black underscoring this concern.”
Hoskins and team already shed doubt on the validity of this test in non-Hispanic Black women in previous work, but in this study, they wanted to assess how accurate the 21-gene breast recurrence score is for “predicting chemotherapy benefit as recommended in the current NCCN Guidelines for Breast Cancer among women from diverse racial/ethnic groups.”
Overall, the study included 6,003 women who were of Asian/Pacific Islander ancestry, 5,697 who were non-Hispanic Black, 6,688 who were Hispanic, and 54,945 who were non-Hispanic White. All the women had ER-positive, HER2-negative breast cancer without axillary lymph node metastases.
According to the 21-gene breast recurrence scores, all women with a score of 26–100 had reductions in risk for death from their cancer with chemotherapy treatment ranging from 20–50% depending on ethnicity. In women with a score on the recurrence test of 11–25, there was no significant benefit on risk for death from breast cancer with chemotherapy.
However, when the groups were stratified by age, Black women aged 50 years or younger had a different reduction in risk than White women. The team carried out an exploratory analysis to assess whether the cut-off score to determine whether someone is eligible for chemotherapy should be lower in Black women and the results suggested that it should.
More work is needed to confirm these results, but the researchers suggest this difference could be because women with this kind of cancer usually receive estrogen blocking treatment as well as possible chemotherapy and the estrogen blocking treatment has less impact on breast tumors in Black compared with White women potentially making chemotherapy more valuable in this group.
“If confirmed, the recurrence score 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. 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,” conclude the authors.
