HER2-Targeted Therapies

About 20% of patients diagnosed with breast cancer will have a specific type of tumor called HER2-positive breast cancer. HER2-positive breast cancers are breast tumors with high levels of a protein called human epidermal growth factor 2 (HER2). HER2 is a protein that functions as a receptor outside of breast cancer cells. When HER2 receives an activating signal from the body, it promotes cell growth and multiplication. As such, HER2-positive breast cancers may grow quickly and have a high chance of spreading to other parts of the body (metastasis).

Treatment of HER2-positive breast cancer often involves a combination of surgery, chemotherapy, and radiation therapy, but with the addition of medications that target HER2, also called HER2-targeted therapies. These targeted therapies can be given before, during or after chemotherapy. They generally don't cause the side effects common with chemotherapy such as nausea, vomiting or hair loss. However, HER2-targeted therapies have unique side effects. A possible side effect involves the heart and is called cardiotoxicity.

The form cardiotoxicity takes can range from temporary changes in heart function that you might not notice to more serious conditions such as heart failure. It also can be life threatening.

Why do HER2-Targeted Therapies Cause Cardiotoxicity?

HER2-targeted therapies block HER2 receptors from receiving signals that tell the cells to grow and multiply. Blocking HER2 on cancer cells is good because it stops the message telling tumor cells to grow and spread. However, HER2 receptors are also on healthy cells, such as heart muscle cells. In the heart, HER2 activation is important for cell survival, particularly during stressful situations, and thus blocking HER2 may cause heart damage.

Author: Roberta Florido, MD
Reviewers: Karen Smith, MD; Debra Madden, BA