How Triple-Negative Breast Cancer Behaves and Looks

To understand triple-negative breast cancer, it’s important to understand “receptors,” which are proteins found on the surface of many breast cancer cells. These receptors enable the cells to receive signals to grow.

• Hormone receptors receive growth signals from the hormones estrogen and progesterone. About 75% of women with breast cancer have cancer cells that are estrogen-receptor-positive, and about 65% have cells that are both estrogen- and progesterone-receptor-positive.
• A smaller percentage of breast cancers — about 20-30% — have too many HER2 receptors (human epidermal growth factor receptor). HER2 receptors receive signals that stimulate the growth of breast cancer cells. The more HER2 receptors the cancer cells have, the more likely the breast cancer is to grow.

Hormonal therapies and HER2-targeted therapies interfere with these signals and stop cancer cells from getting the messages to grow.

About 10-20% of breast cancers are found to be triple-negative. Having triple-negative breast cancer means that, in the lab, your cells tested negative for hormone receptors and HER2 receptors. Therefore, the cancer will not respond to hormonal therapies, including tamoxifen, Arimidex (chemical name: anastrozole), Aromasin (chemical name: exemestane), Femara (chemical name: letrozole), and Faslodex (chemical name: fulvestrant). Triple-negative breast cancer also will not respond to medications that target HER2, such as Herceptin (chemical name: trastuzumab) or Tykerb (chemical name: lapatinib). However, triple-negative breast cancer can be treated with chemotherapy and radiation therapy.

In addition, triple-negative breast cancer:

• Tends to be more aggressive than other types of breast cancer. Studies have shown that triple-negative breast cancer is more likely to spread beyond the breast and more likely to recur (come back) after treatment. These risks appear to be greatest in the first few years after treatment. For example, a study of more than 1,600 women in Canada published in 2007 found that women with triple-negative breast cancer were at higher risk of having the cancer recur outside the breast — but only for the first 3 years. Other studies have reached similar conclusions. As years go by, the risks of the triple-negative breast cancer recurring become similar to those risk levels for other types of breast cancer.
  Five-year survival rates also tend to be lower for triple-negative breast cancer. A 2007 study of more than 50,000 women with all stages of breast cancer found that 77% of women with triple-negative breast cancer survived at least 5 years, versus 93% of women with other types of breast cancer. Another study of more than 1,600 women published in 2007 found that women with triple-negative breast cancer had a higher risk of death within 5 years of diagnosis, but not after that time period. The recurrence and survival figures in these and other studies are averages for all women with triple-negative breast cancer. Factors such as the grade and stage of the breast cancer will influence an individual woman’s prognosis.
• Tends to be higher grade than other types of breast cancer. The higher the grade, the less the cancer cells resemble normal, healthy breast cells in their appearance and growth patterns. On a scale of 1 to 3, triple-negative breast cancer often is Grade 3.
• Usually is a cell type called “basal-like.” “Basal-like” means that the cells resemble the basal cells that line the breast ducts. This is a new subtype of breast cancer that researchers have identified using gene analysis technology. Like other types of breast cancer, basal-like cancers can be linked to family history, or they can happen without any apparent family link. Basal-like cancers tend to be more aggressive, higher grade cancers — just like triple-negative breast cancers. It’s believed that most triple-negative breast cancers are of the basal-like cell type.

It is perfectly natural to feel concerned when you learn you have a form of breast cancer that (1) is often more aggressive than other types and (2) does not respond to treatments such as hormonal therapy and Herceptin. However, remember that triple-negative breast cancer is a treatable disease. Researchers also are paying a great deal of attention to triple-negative breast cancer and working to find new and better ways to treat it. More and more people are talking about triple-negative breast cancer, which should make it easier to find other women who share your concerns.