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Triple Negative Breast Cancer

“Triple negative” is the term used to describe tumors that are ER-negative, PR-negative, and HER2-negative. It’s estimated that about 20% of breast tumors are triple negative.

These tumors do not respond to hormone therapy or HER2-targeted therapies. They do, however, respond well to chemotherapy. Also, many clinical trials  are now underway looking at new treatments for triple negative tumors.

Studies have found that African-American women appear more likely to develop triple-negative tumors than women of other ethnic backgrounds. They are also more common among women who carry a BRCA1 mutation.

A tumor that is ER-negative and PR-negative will not respond to hormone therapy and because it is HER2-negative it can’t be  treated with HER2-targeted therapies. In general, HER2-positive tumors are more aggressive than other tumor types. However, Herceptin’s use in the adjuvant setting has somewhat leveled the playing field. So, while being triple negative means you can’t take Herceptin, it’s actually not a bad thing in and of itself that your tumor is HER2-negative.

This means the primary systemic treatment is chemotherapy. However, since 2006, studies have suggested that women with early stage ER-negative tumors have benefited more from new chemotherapy regimens than women with ER-positive tumors. As a result, women with early stage ER-negative tumors now have a prognosis nearly as good as that of women with ER-positive tumors. In addition, there are many clinical trials underway looking at new treatment options for patients with triple negative breast cancer.

Some articles you see may use the terms "triple negative" and "basal-like" interchangeably, but they really shouldn't. Not all triple-negative tumors have the unique characteristics that define basal-like tumors. (They are called basal-like because these cancers begin in the basal cells that line the breast ducts.) Further, while most basal-like tumors are triple-negative, they aren't always.

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