Triple Negative Breast Cancer
About 10 to 20 percent of breast cancers are classified as triple-negative. Having triple-negative breast cancer means that cells test negative for estrogen receptor (ER), progesterone receptor (PR), and HER2 receptors. This cancer will not respond to hormonal therapies, including tamoxifen, Arimidex, Aromasin, Femara, and Faslodex, or to medications that target HER2, such as Herceptin or Tykerb.
Triple Negative breast cancer (TNBC) is a significant health problem from the standpoint that 11 percent of Caucasians, 17 percent of Hispanics, and 25 percent of African-Americans have this type of breast cancer. Women who carry a BRCA1 mutation typically develop these types of tumors as well. Some clinical trials are comparing the effectiveness of various older and newer chemotherapy medications, used in different combinations, for treating this type of breast cancer.
PARP (poly ADP-ribose polymerase) inhibitors
The PARP (poly ADP-ribose polymerase) enzyme fixes DNA damage in cells, including DNA damage caused by chemotherapy medicines. PARP inhibitors were developed based on the idea that a medicine that interferes with or inhibits the PARP enzyme might make it harder for cancer cells to fix damaged DNA, which could make chemotherapy more effective. A recent small study of women with advanced triple-negative breast cancer found that those taking the PARP inhibitor called iniparib along with chemotherapy survived longer than those who took chemotherapy alone. Other small studies showed some benefit for using another PARP inhibitor, olaparib, in combination with chemotherapy for triple-negative breast cancer.
VEGF (vascular endothelial growth factor) inhibitors
To get the oxygen and nutrients they need to grow and spread, tumors create new blood vessels through a process called angiogenesis. Avastin (chemical name: bevacizumab) is a medicine that interferes with the activity of the VEGF protein, which stimulates this process. Avastin attaches itself to VEGF, preventing VEGF from interacting with receptors on the blood vessels. By blocking this interaction, Avastin keeps VEGF from stimulating angiogenesis.
EGFR (epidermal growth factor receptor)-targeted therapies
Other treatments target epidermal growth factor receptor, or EGFR. Many triple-negative breast cancer cells are known to “overexpress” EGFR. These receptors receive signals that spur the growth of the cancer. Erbitux (chemical name: cetuximab) is a medication that attaches to the EGFR. When this happens, growth signals can’t attach to EGFR on the cancer cell, and so they cannot stimulate the cell to grow.
Clinical trials using these and other therapies could play a key role in improving the treatment of triple-negative breast cancer.