Vaccine Treatment for Metastatic Breast Cancer

Medically Reviewed by Gabriela Pichardo, MD on June 12, 2022
3 min read

You may think of vaccines as a way to prevent disease, but researchers are testing a new kind that might help treat breast cancer. It works by activating the immune system -- your body's defense against germs -- to find and kill cancer cells.

Treatment for metastatic breast cancer usually involves some combination of chemotherapy, hormone therapy, and targeted drugs. Immunotherapy, which stimulates your immune system to fight cancer, is sometimes also an option for some types of breast cancer. At this late stage, the cancer can't be cured, but treatments like these can slow its spread and help you live longer.

The hope for vaccines is that they could one day create long-term action by the immune system to attack breast cancer cells, with fewer side effects than current treatments like chemotherapy. The FDA has not yet approved any vaccines to treat breast cancer. Researchers are studying the vaccines in clinical trials to check their safety and see how well they work.

Breast cancer vaccines are a type of immunotherapy -- treatments that help your body fight off cancer.

Your immune system is designed to find and destroy cancer and other abnormal cells on its own. But sometimes, cancer cells can hide from your immune system or make it act so weakly that it can't fight them off.

Cancer vaccines contain proteins, DNA, or other pieces of cancer cells. Scientists change these substances in a lab and then put them back into your body so they can "teach" your immune system to attack the cancer.

Cancer cells contain proteins called antigens on their surface. Most cancer vaccines contain an antigen that helps your immune system recognize the cancer as foreign. When your immune system "sees" these antigens, it makes its own proteins, called antibodies, to destroy the cancer cells.

Many vaccines add an adjuvant -- a substance that boosts the action of your immune system against the cancer.

Another type of vaccine uses your own immune cells to fight the cancer. Doctors take these cells from a sample of your blood and then alter them in a lab so they can find and kill cancer once they go back into your body.

Adding another drug may help cancer vaccines work better. In the future, it's possible that breast cancer vaccines might be combined with the HER2-positive breast cancer drug trastuzumab (Herceptin), chemotherapy drugs, or radiation therapy.

Vaccines are a more targeted way to treat breast cancer than radiation and chemotherapy. They focus on killing cancer cells without harming healthy ones.

By contrast, chemotherapy kills quickly-dividing cells -- both cancer cells and some healthy cells like hair and immune cells. That's why it causes side effects like hair loss, infections, and mouth sores.

There aren't any breast cancer vaccines available yet, but a few are in clinical trials -- studies that test whether new treatments work and if they're safe.

A vaccine called NeuVax is furthest along in the research. It treats HER2-positive breast cancer, a type that contains a protein called human epidermal growth factor receptor 2 (HER2). Up to 30% of breast cancers make HER2 in large amounts, which helps the cancer cells grow.

NeuVax has small pieces of HER2 protein in it, along with an adjuvant. Sometimes, researchers combine NeuVax with the drug trastuzumab to help it work better against the cancer.

In studies, NeuVax boosted the immune system action against HER2-positive breast cancer. We still don't know whether the vaccine helps people with this cancer live longer, but researchers aim to find out in future clinical trials.

Another type of breast cancer vaccine infects the cancer cells with a virus that is altered so it doesn't make you sick. Instead, it triggers your immune system to attack the cancer.

A few other breast cancer vaccines are also in clinical trials. Joining one of these trials could be a way for you to try a new vaccine before it's available to the public.

Ask the doctor who treats your cancer if a clinical trial of a breast cancer vaccine or other treatment might be right for you.