How does HER2-targeted therapy work for HER2 breast cancer?

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HER2-positive breast cancer is a breast cancer that tests positive for a protein called human epidermal growth factor receptor 2 (HER2). This protein promotes the growth of cancer cells. In about one of every five breast cancers, the cancer cells have extra copies of the gene that makes the HER2 protein.

The treatment of HER2-positive breast cancer will depend on your preferences as well as the characteristics of your cancer:

Many women with HER2-positive breast cancer will get neoadjuvant chemotherapy first, along with medication that targets HER2 directly. Following surgery, these women will get additional (adjuvant) therapy with HER2-directed medication.

Some women (particularly those with smaller tumors) will get surgery first, followed by adjuvant therapy consisting of both chemotherapy and HER2-directed therapy.

Women whose cancer is "hormone receptor-positive," meaning it requires estrogen to grow, may also be offered endocrine therapy.

Chemotherapy is not given every day but instead is given in cycles of typically 14 or 21 days. When given as adjuvant therapy, it is usually started within four to six weeks after surgery and before radiation therapy. The most common side effects are nausea, vomiting, mouth soreness, hair loss, and a decrease in the number of white blood cells (which can raise your risk of infection). Long-term side effects can include premature menopause (ovarian failure), damage to the heart, and a small risk of leukemia.

Most women with HER2-positive breast cancer will receive one or more chemotherapy drugs in addition to Trastuzumab, the anti-HER2 antibody. Trastuzumab and chemotherapy are even recommended for women with very small, HER2-positive breast cancers. Tumors as small as 0.20 inches often warrant such treatment. However, decisions must be individualized based on your own individual risk. The most common side effect of Trastuzumab is fever and/or chills. Heart failure develops in approximately three to five percent of women treated with Trastuzumab. However, trastuzumab-related heart damage may not be permanent.

Some women also get a second medication, Pertuzumab (monoclonal antibody), along with Trastuzumab (monoclonal antibody). However, Pertuzumab is associated with side effects, including diarrhea, anemia (having too few red blood cells), and neutropenia (low levels of neutrophils, which are a type of white blood cell).

Another option for certain women is a medication that combines Trastuzumab with a drug called Emtansine (this combination drug is called T-DM1). This can be given to women who received neoadjuvant therapy (before surgery) with chemotherapy and Trastuzumab but still have residual disease at the time of surgery.

I hope this information helps provide some insight into your symptoms.

Please do not hesitate to reach out if you have any further questions or concerns.

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