Test May Be ‘Misguiding’ Breast Cancer Treatment for Black Women

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The 21-gene breast recurrence score may lead clinicians away from prescribing chemotherapy to Black women who could benefit from the therapy.

Black woman holding a pink ribbon in her hands, symbolizing breast cancer.

Utilizing a specific biomarker test may not be the most beneficial approach for Black women with breast cancer, a study found.

A common test used to inform breast cancer care decisions may be making wrong treatment recommendations for Black women, according to recent research published in the Journal of the National Comprehensive Cancer Network.

The researchers from the study analyzed data from more than 73,363 women with early-stage, estrogen receptor (ER)-positive breast cancer who underwent the 21-gene breast recurrence score, which is the most commonly ordered biomarker test for this patient population. More specifically, the test lends insight into the prognosis of patients, as well as how effective post-surgical chemotherapy is. The goal is to mitigate the use of unnecessary chemotherapy.

However, these findings showed that test results are actually underestimating the potential benefit of chemotherapy for Black women — and younger black women, in particular — who may benefit from the treatment.

“This test could be misguiding treatment,” study author, Dr. Kent Hoskins, a professor of oncology at the University of Illinois Chicago, said in a news release about the findings.

The standard-of-care treatment for ER-positive breast cancer is estrogen blockade, with or without chemotherapy (a decision that is guided by the 21-gene breast recurrence score). However, Black women may be less likely to respond to this type of hormone therapy and could experience more benefit from the addition of chemotherapy, according to the study authors.

In fact, another study published in 2018 in the journal, Breast Cancer Research and Treatment, found a racial disparity in survival for women with ER/progesterone-receptor (PR)-positive breast cancer, regardless of tumor stage, grade or therapy, “suggesting that there may be racial differences in the molecular characteristics of hormone receptor-positive tumors, such that ER/PR positive tumors in black patients may be less responsive to standard treatments.”

That said, the researchers of this recent study believe that the test cutoffs that determine chemotherapy treatment may need to be scrutinized and evaluated for each patient, especially as Black individuals were found to have a higher likelihood of breast cancer-related death compared to other races when analyzed by age (those 50 years or younger and those 51 years or older).

Findings showed that Black and Hispanic women aged 50 or younger tended to have a larger reduction in breast cancer death with the addition of chemotherapy, compared to White women of the same age. For women 51 years or older, chemotherapy-containing regimens were associated with a decreased risk of death only among Black women.

“The research shows that it may be inappropriate for doctors to use exact cutoffs and tests, regardless of race or ethnicity because there are underlining differences in biology,” Hoskins said.

Hoskins noted that while research suggests that these biological differences exist, that does not discount the effects that social factors, such as structural racism and access to care, have on breast cancer outcomes in Black women. The news release mentioned that these same social determinants of health may also cause molecular differences in the tumors. The research team is working on another study looking at this question.

“We believe that it’s actually the same forces that lead to inequities in care that are driving this more aggressive biology,” Hoskins said.

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