DNA testing can help right racial imbalance in breast cancer

Routine genomic testing could correct well-established disparities in breast cancer survival rates between white and black women, according to a new study.

Black women have a 5% lower incidence of breast cancer compared to white women in the US, but have a 40% higher mortality rate, with the imbalance in outcomes even after controlling for socioeconomic factors and despite similar treatment regimens.

The observational study, published in the Nature journal npj Breast Cancer, looked at the effects of genomic testing using tumour analyses supplied by US-Netherlands medtech firm Agendia – MammaPrint and BluePrint – in more than 1,000 black and white women with HR-positive, HER2-negative early breast cancer, matched for age and menopausal status.

The researchers, led by Sonya Reid, an assistant professor of medicine at Vanderbilt University Medical Center in the US, found that black subjects were twice as likely to have more aggressive tumours – which are often missed with standard testing – compared to white counterparts.

However, despite the differences in the severity of their cancer, three-year outcomes were the same when they were treated according to their genomic test results, suggesting that the analyses were reducing the under-treatment of black women, improving their clinical outcomes and reducing the risk of their cancer returning after treatment.

In a subgroup of black women enrolled in a US breast cancer registry called BEST, women deemed to have low-risk tumours using the MammaPrint test had a 97.7% recurrence-free rate after 10 years, the same outcome as white women.

William Audeh, Agendia's chief medical officer and a co-author of the study, said: "The risk of recurrence of breast cancer in Black women has often been underestimated by traditional clinical features, driven largely by their underrepresentation in clinical trials."

"By providing a genomic assessment of tumour biology, we can ensure that women with breast cancer will receive individualised care that improves their long-term outcomes," said Audeh.

A 2022 study looking at 15 years of cancer trial reports in the US found that almost half (48%) had no Hispanic or Latin American subjects, and 42% had no black patients, exposing the ongoing challenges in making sure studies accurately reflect the real-world situation in US cancer treatment.

Reid said the findings underscore a critical need to move beyond standard clinical markers, such as hormone receptor staining, for identifying higher-risk breast cancer types and guiding "more tailored, personalised care."

She added that the aggressive tumours detected using the genomic testing "demonstrate clinical behaviour similar to triple-negative breast cancer and may warrant more aggressive treatment."