HER2-Positive Metastatic Breast Cancer Treatment Options Explained

If you are diagnosed with HER2-positive breast cancer it means you likely have high levels of the HER2 protein on the outside of your cancer cells. Having metastatic HER2 positive breast cancer means that not only is the HER2 receptor present on the outside of the cell, but that the cancer has spread beyond the breast.

“So that means that the breast cancer is living in another part of your body,” says Dr. Elizabeth Comen, a medical oncologist from the Memorial Sloan Cancer Center in New York. She goes on to explain “That can be in the liver, the bone, the lungs or potentially even the brain.”

Therapies that Target the Receptor

Targeted therapy is a treatment that targets specific genes, proteins, or the tissue environment that contribute to the cancer’s development and growth. There are specific targeted therapies meant to treat HER2 positive cancers, that are used in metastatic breast cancer. “The good news is that there are a lot of new treatments available that target the HER2 receptor,” says Dr. Comen.

These include Herceptin and pertuzumab, which can be used together with chemotherapy and are usually used as front line treatments. That means it will be the first treatment you receive, says Dr. Comen.

Another drug that used is T-DM1, which is used if you have already been treated with Herceptin. The exciting news is that there is another new drug available called Tucatinib, which is now available for women who have not responded to Herceptin or pertuzumab.

Crossing the Blood-Brain Barrier

There is a new drug for women who may have had their disease get worse after receiving Herceptin, Pertuzumab, or T-DM1. This drug is Tucatinib. “The important thing to know about Tucatinib—and that’s really exciting—is that it has been shown to have some benefit for patients with brain metastasis,” says Dr. Comen.

The current medications used to treat HER2 positive breast cancer do a good job of controlling the disease below what’s known as the “the blood-brain barrier.” But this barrier prevents many drugs from reaching the brain, making it difficult to control brain metastasis. Instead, surgery and radiation therapy have traditionally been used to treat brain metastasis when it occurs.

“It is really exciting to have newer drugs on the market that can penetrate the brain and improve outcomes for patients with brain metastasis,” says Dr. Comen.

However, despite the potential for newer drugs to cross the blood-brain barrier, in patients with known brain metastasis it is still important to be evaluated by a surgeon and radiation oncologist to help with treatment recommendations.

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