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Androgen receptor expression uncommon in black women with triple-negative breast cancer
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Black women with triple-negative breast cancer appeared more likely to lack the androgen receptor protein compared with white women, according to study data presented at the AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved.
This difference in androgen receptor expression may contribute to the racial disparity observed among black women with triple-negative breast cancer, according to the researchers.
Androgen receptor is a nuclear steroid hormone receptor that is expressed in 10% to 43% of triple-negative breast cancers and has demonstrated potential as a biomarker for this disease.
“Studies have shown that androgen receptor signaling can influence the tumor biology of triple-negative breast cancer, but there are conflicting reports about the influence of androgen receptor on clinical outcomes,” Shristi Bhattarai, a PhD student at Georgia State University, said in a press release.
Because black women are more likely to be diagnosed with triple-negative breast cancer at a young age and experience more aggressive disease, Bhattarai and colleagues conducted immunohistochemistry in formalin-fixed paraffin-embedded samples from 822 patients to evaluate racial trends in androgen receptor expression. Of the patients, 138 were black and 675 were European-American.
Researchers defined samples with less than 1% nuclear-stain cells positive for androgen receptor as “quadruple negative,” or negative for ER, PR, HER-2 and androgen receptor.
In total, 45.6% of patients were quadruple negative. Quadruple negativity occurred in a significantly greater proportion of black than white patients (80.8% vs. 40.1%; P < .0001).
Univariate analyses showed patients with quadruple-negative status were more likely to be younger than 25 years of age at diagnosis, be black and have higher proliferative index (KI > 14%; P < .001 for all).
Multivariate analyses that adjusted for grade, stage and adjuvant therapy showed loss of androgen receptor expression increased risk for mortality (HR = 2.8; P < .05).
Researchers acknowledged that information about race was self-reported, and data were lacking on patients’ ancestry genotype information, which could help broaden the understanding between genetic ancestry, androgen receptor status and tumor biology of triple-negative breast cancer.
“Since androgen receptor can serve both as a predictive as well as prognostic biomarker, routine screening of androgen receptor along with ER, PR and HER-2 may be beneficial,” Bhattarai said. “Our study shows that genetic ancestry and androgen receptor 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.” – by Alexandra Todak
Reference:
Bhattarai S, et al. Abstract B12. Presented at: AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; Sept. 25-28, 2016; Fort Lauderdale, Fla.
Disclosure: The study was funded by NIH. Bhattarai reports no relevant financial disclosures.