Targeted HER2 Therapy

What Is Targeted HER2 Therapy?

Targeted HER2 therapies are treatments that target a specific protein called HER2/neu that allows the cancer cells to grow in a rapid or abnormal way. Targeted therapies are generally less likely than chemotherapy to harm normal, healthy cells. However, they are more effective when given in combination with chemotherapy.

How does it work?

There are currently four HER2 targeted therapy drugs that doctors use to treat breast cancer:

• Herceptin (trastuzumab) works against HER2-positive breast cancers by blocking the ability of the cancer cells to receive chemical signals that tell the cells to grow.
• Tykerb (lapatinib) works against HER2-positive breast cancers by blocking certain proteins that can cause uncontrolled cell growth.
• Perjeta (pertuzumab), similar to Herceptin, works against HER2-positive breast cancers by blocking the cancer cells’ ability to receive growth signals.
• Kadcyla (T-DM1 or ado-trastuzumab emtansine) is a combination of Herceptin and the chemotherapy medicine emtansine. Kadcyla was designed to deliver emtansine to cancer cells in a targeted way by attaching emtansine to Herceptin. Herceptin then carries emtansine to the HER2-positive cancer cells, thus potentially making the chemotherapy more effective while being less toxic to normal cells.

Who needs targeted HER2 therapy?

• Invasive breast cancer – approximately 20% of invasive breast cancers are HER2 positive, meaning they have too many copies of the HER2 gene. This results in HER2 overexpression, or too much HER2 protein on the cell’s surface. This leads to a cancer cell receiving lots of signals to grow, thus resulting in a cancer cell which can grow or spread more quickly.
• Ductal carcinoma in situ (DCIS) – studies show up to 60% of DCIS are HER2 positive, but the clinical significance of this is unknown. In the NSABP B-43, doctors are currently studying whether adding a targeted drug (Herceptin) during radiation therapy after lumpectomy may help reduce the risk of a local recurrence.

When is targeted therapy given?

Like chemotherapy, targeted HER2 therapy can be given either after surgery or before and after. Your doctors will help you decide which timing is best for you.

What are the side effects of targeted HER2 therapy?

Targeted therapies are generally given with chemotherapy, so patients still experience side effects of chemo. Rare side effects which are specifically associated with targeted therapies include damage to the heart muscle and swelling of lung tissue. Report any symptoms of shortness of breath, difficulty breathing, a fast or irregular heartbeat, increased cough, and swelling of the feet or lower legs to your doctor as soon as possible.