Examining Disparities in Triple-Negative Breast Cancer

The lack of androgen receptor protein may contribute to racial disparities in survival for women with this aggressive form of breast cancer.

Triple-negative breast cancer is an aggressive form of the disease that has a higher prevalence and worse prognosis in African-American women compared with women of European descent.

A study presented in September 2016 at the AACR Cancer Health Disparities conference in Fort Lauderdale, Florida, showed that triple-negative breast cancer in African-American women is much more likely to lack the androgen receptor protein compared with the disease in European- American women. This difference, the study suggests, may contribute to the racial disparity in survival outcomes among these two populations.

A major characteristic of triple-negative breast cancers is that these cancers do not express any of the three proteins – estrogen receptor (ER), progesterone receptor (PR), and Her2/neu – which can be targeted by available therapies. Thus women with this form of the disease have high recurrence and mortality rates, especially within the first five years after diagnosis, explained study lead author Shristi Bhattarai, a PhD student working under the supervision of Ritu Aneja, PhD, at Georgia State University in Atlanta.

“Studies have shown that androgen receptor (AR) signaling can influence the tumor biology of triple-negative breast cancer, but there are conflicting reports about the influence of AR on clinical outcomes,” said Bhattarai.

“In our study, the triple-negative breast cancers in African-American women tended to be AR-negative, and multivariable analyses showed that the loss of AR expression was associated with poorer survival,” Bhattarai said. “The higher prevalence of quadruple-negative breast cancer [lack of ER, PR, HER2/neu, and AR] among African-Americans may be a plausible contributor to the ethnic disparity in outcomes among triple-negative breast cancer patients.

“We are excited about our findings because one of the biggest questions confronting clinicians and researchers pertains to the inherent differences in the tumor biology between the triple-negative breast cancers in African-American and European-American women,” she added.

For their study, Bhattarai and colleagues used breast cancer samples from 813 triple-negative breast cancer patients treated at Emory, Northside, or Grady Memorial Hospitals in Atlanta, or at Nottingham Hospital in the United Kingdom, for whom complete clinicopathologic data, overall survival, and ethnicity information were available.

“Our study shows that genetic ancestry and AR status are key factors that should be taken into consideration while designing and enrolling patients for clinical trials aimed at finding new targeted therapies for triple-negative breast cancer patients,” Bhattarai added.

This study was funded by the National Institutes of Health.