A Review of Triple-negative Breast Cancer

Roohi Ismail-Khan, MD; Marilyn M. Bui, MD, PhD

Disclosures

Cancer Control. 2010;17(3):173-176. 

In This Article

Epidemiology

An estimated 1 million cases of breast cancer are diagnosed annually worldwide.[3] Of these, approximately 170,000 are of the triple-negative (ER–/PR–/HER2–) phenotype.[3] Of these TNBC cases, about 75% are "basal-like."[4] The prevalence of TNBC is highest in premenopausal African American women; a recent report notes that 39% of all African American premenopausal women diagnosed with breast cancer are diagnosed with TNBC.[5] The prevalence of TNBC in this same age group in non–African American women is much less, at approximately 15%. These ethnic or menopausal differences are not seen in either the ER+/HER2+ breast cancer subgroup or the ER+/HER2− subgroup.[5]

Multiple other studies and abstracts have confirmed that TNBC occurs in a higher percentage of African American women. Of these TNBC cases, about 75% are also of the basal-type molecular classification. As presented initially in 2006 at the San Antonio Breast Cancer Symposium in a study of racial differences in the prevalence of triple-negative invasive breast tumors, researchers found that the incidence of triple-negative disease among African American women was more than twice that among white women. They also reported that 47% of tumors in African American women were "triple-negative" compared with 22% in white women. After adjusting for age and stage at diagnosis, African American women were almost 3-fold more likely than white women to have triple-negative tumors.[2]

These disparities in incidence among different racial groups leads us to question whether genes or mutations predispose women, particularly premeno pausal African American women, to TNBC. Studies have shown that breast cancers in women with germ-line BRCA1 mutations are more likely to be triple-negative and high-grade.[6] Gene expression studies have confirmed this phenomenon and also that BRCA1-associated breast cancer appears to cluster in the basal-like subtype.[7]

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