Racial Differences in 21-Gene Recurrence Scores Among Patients with Hormone Receptor-Positive, Node-Negative Breast Cancer

Authors: Holowatyj, A.N. et. al.
Source: http://ascopubs.org/doi/full/10.1200/JCO.2017.74.5448

The differences in breast cancer outcomes between black and white women are being studied with increasing frequency. Investigators are trying to understand the causes of these differences. Some causes, such as socioeconomic status and access to care, have very clear links. Other causes, such as factors of tumor biology, are not as straightforward to understand.

The 21-gene RS assay reviews specific genetic features of tumor cells. It then predicts the risk (low, intermediate or high) of breast cancer recurrence with and without chemotherapy. This information guides providers in making treatment recommendations for their patients. The authors of this study looked at differences in RS assay results between white and black women as a means to explain differences in outcomes.

The Metropolitan Detroit Cancer Surveillance System registry was accessed for this study. The investigators selected non-Hispanic black and white women with hormone receptor-positive, HER2-negative, node-negative invasive breast cancer who had RS results available. More than 2,200 women were included.

Black women tended to present with higher grade and larger cancers. The mean RS value among black women was in the intermediate risk range (18-30), while the mean score among white women was in the low risk range (<18). Black women were likely than white women to have RS results in the high risk range (≥31). Black women were more likely to have high risk RS results if they were under age 65.

When the investigators adjusted the data to account for differences in age, stage, tumor grade and tumor histology, black women still remained more likely to have high-risk RS values.

This study supports the notion that the differences in breast cancer outcomes between black and white women are caused by multiple factors. Specific biology of the disease and the physical environment of a woman’s body appear to play significant roles, and more investigation into this topic is needed. Additionally, it is important to consider that the 21-gene assay needs to be studied more closely among women of color.