How is HER2-positive breast cancer treated?

About 25 to 30 percent of women with breast cancer have an excess of a protein called HER2, which makes tumors grow quickly. Two genetically engineered drugs, trastuzumab (Herceptin) and lapatinib (Tykerb), bind to HER2 to help fight cancer cells. Trastuzumab was initially approved for treatment of metastatic breast cancer, but it has since been approved for adjuvant therapy (meaning it can be used in addition to other types of therapy, such as surgical excision or radiation) of early breast cancer. The more recently approved lapatinib is used in combination with another cancer drug called capectabine (Xeloda).

Stacy Wiegman, PharmD
Pharmacy Specialist

The Food and Drug Administration (FDA) has approved five drugs for HER2-positive breast cancer:

  • Herceptin (trastuzumab) is used for both early-stage HER2-positive breast cancer and HER2-positive breast cancer that has spread beyond the breast (also called metastatic breast cancer). It's injected into a vein and is usually used in combination with chemotherapy. Kadcyla (ado-trastuzumab emtansine) is a targeted therapy based on Herceptin, which has been found to have fewer side effects.
  • Tykerb (lapatinib) is used to treat advanced or metastatic breast cancer in people who have had other types of treatment already. It's a pill used in combination with a chemotherapy drug called capecitabine (Xeloda).
  • Perjeta (pertuzumab) is used to treat metastatic HER2-positive breast cancer that has not been treated previously. It's used in combination with trastuzumab and the chemotherapy medication docetaxel.

Perjeta, Herceptin and Tykerb all aim at the HER2 protein (receptor) in order to slow or stop the growth of cancer cells, but they bind to different parts of the receptor and seem to have slightly different effects. Tykerb can sometimes be prescribed to people who have not responded to Herceptin or who have developed a resistance to that drug. Tykerb also appears to be more successful at treating HER2-positive breast cancer that has spread to the brain. Research is under way to see if combining these two drugs into one therapy can improve the outcomes in people with HER2-positive breast cancer. The combination of Perjeta and Herceptin with docetaxel extended life by about six months in some studies. Nerlynx (neratinib) is a tablet prescribed as the first extended adjuvant therapy for HER2-positive cancer; it is used after the initial treatment to prevent the cancer from returning. It is given with loperamide to prevent diarrhea.

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