About 20% of breast cancer patients have HER2 positive disease. HER2 is a protein expressed on the cell membrane. In patients with HER2 positive breast cancer, much more HER2 is expressed than usual. This ensures that the cancer cells grow and divide quickly. HER2-positive breast cancer is therefore associated with an aggressive course and a poorer prognosis in patients who do not receive (neo-) adjuvant treatment. This means that patients with HER2 positive breast cancer are almost always treated with chemotherapy in combination with HER2-targeted therapy (which significantly improves the prognosis).
Trastuzumab (Herceptine®) is a monoclonal antibody directed against HER2. In HER2 positive breast cancer, it is often associated with chemotherapy treatment. It is administered subcutaneously once every 3 weeks for a total treatment duration of 1 year. Usually it is well tolerated. The main side effect is a decrease in the pumping function of the heart. Usually this is asymptomatic and we see a spontaneous recovery if treatment is interrupted.
Pertuzumab (Perjeta®) is another monoclonal antibody directed against HER2. It can be associated with treatment with trastuzumab in patients, including cancer cells in the axillary glands.
Trastuzumab-Emtansine (Kadcyla®) is a third product. It is an "antibody drug conjugate". This means that it is an antibody (in this case Trastuzumab) which is linked to a certain type of chemotherapy (in this case Emtansine). It is currently used in women in whom tumor cells are found during surgery after neoadjuvant treatment (chemotherapy with trastuzumab and pertuzumab or not). Trastuzumab-Emtansine is administered intravenously every three weeks, usually for 14x in total. It is often well tolerated.
The most common side effects are a decrease in blood platelets, an increase in liver values in the blood, tingling in the fingers and toes, fatigue and gastrointestinal discomfort.