In metastatic breast cancer, or stage IV disease, the cancer cells have traveled from the breast and nearby lymph nodes and formed tumors in tissues or organs far away from the breast. Metastatic breast cancer can be:
- Hormone receptor-positive
- Both hormone receptor-positive and HER2-positive
If you are diagnosed with metastatic HER2-positive breast cancer, it means the stage IV breast cancer can be treated with HER2-targeted therapy. You can find more information on how metastatic breast cancer is diagnosed on our pages about Metastatic Breast Cancer and Testing.
If you had early-stage HER2-positive breast cancer, the metastasis is likely to be HER2-positive as well. Your medical oncologist may recommend you have a biopsy of any abnormal finding from an imaging test. The biopsy helps to:
- diagnose the cancer
- confirm the cancer is metastatic
- check the receptor status to make sure it did not change from your original diagnosis
Metastatic HER2-positive breast cancers are more likely than other types of disease to spread to the brain and spinal cord, which with the spinal fluid make up the central nervous system or CNS. Up to half of people diagnosed with HER2-positive metastatic breast cancer develop metastases to the central nervous system. There are local therapies available to treat these metastases.
Treatment of HER2-positive breast cancer that has spread to organs other than the brain usually includes medicines that target the HER2 protein and block its actions. These HER2-targeted therapies are:
- Trastuzumab (Herceptin). This medicine can attach to the HER2 proteins and block the signals that tell cells to multiply too quickly, causing cancer. It is often given with chemotherapy.
- Lapatinib (Tykerb). This medicine treats metastatic breast cancer when the standard trastuzumab has stopped working. Like trastuzumab, lapatinib blocks the action of the HER2 protein. But while trastuzumab works on the outside of the cell, lapatinib works on the inside. Lapatinib is given in combination with capecitabine (Xeloda) or, if the cancer is both HER2- and HR-positive, letrozole (Femara).
- Pertuzumab (Perjeta). This medicine works by blocking signals that tell breast cancer cells to multiply.
- Ado-trastuzumab emtansine (Kadcyla). This medicine is an antibody drug conjugate, a medicine that combines a targeted therapy with chemotherapy. Ado-trastuzumab emtansine sends the chemotherapy medicine straight to the cancer cells to prevent healthy cells from being affected.
You may also consider taking part in a clinical trial, a study that looks at how well new medical approaches work in people. Clinical trials offer access to new treatments that are not otherwise available and may prove to work better than standard treatments. Participating in a clinical trial also helps researchers develop better treatments for people diagnosed in the future.
Most systemic, or whole-body, therapies have trouble reaching the brain. Medicines like trastuzumab and pertuzumab are monoclonal antibodies, molecules that have an even harder time than other treatments getting to the brain because of their large size. Researchers are studying small molecules, called tyrosine kinaise inhibitors or TKIs, to see whether they can more easily cross the blood-brain barrier.