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Triple-negative breast cancer (TNBC) is an aggressive type of breast cancer that can be difficult to treat. Immunotherapy is one of the newest types of breast cancer treatment — it uses your own immune system to fight cancer. Currently, pembrolizumab (Keytruda) and sacituzumab govitecan-hziy (Trodelvy) are the only immunotherapies approved by U.S. Food and Drug Administration (FDA) to treat TNBC.
If you or a loved one has been diagnosed with TNBC, continue reading to learn more about these treatment options.
Immunotherapy uses parts of your own immune system or substances made in a laboratory to fight cancer cells.
Your immune system keeps track of all the substances that belong in your body through a collection of organs, specialized cells, and proteins. When your immune system is working well, it can identify and destroy substances that don’t belong, such as viruses and bacteria.
Immunotherapy helps your immune system target and destroy breast cancer cells.
Your immune system can also target cancer cells. However, some cancer cells are able to escape your natural immune defenses and begin growing out of control. Immunotherapy drugs can help boost your immune defenses to target cancer cells.
Some types of immunotherapy boost your immune system’s natural defenses. Other types use laboratory-made substances that mimic parts of your immune system to attack cancer cells.
A biomarker is a protein, gene, or substance in your blood or tissue that is a sign of disease, such as cancer. The results of biomarker testing can give your doctor more information about the type of cancer you have, your outlook, and how likely you are to respond to certain treatments.
If your triple-negative breast cancer cells test positive for the biomarker protein PD-L1, you may respond well to pembrolizumab.
If you have TNBC, your cancer cells lack three common biomarkers — estrogen receptors, progesterone receptors, and the protein HER2. Without estrogen or progesterone receptors, hormonal therapy isn’t effective. TNBC cancer cells also don’t make much of the protein HER2, which allows cancer cells to grow uncontrollably. Anti-HER2 therapies won’t be effective when cancer cells don’t make this protein.
Immunotherapy for TNBC relies on biomarkers other than hormone receptors and HER2. To see if your cancer cells will respond to immunotherapy, your doctor will test your cancer cells for the programmed cell death ligand 1 (PD-L1) protein. Another protein, PD-1, is found on immune cells called T cells. PD-1 and PD-L1 are called checkpoints because they switch off T cells that would normally attack cancer cells.
About 20 percent of TNBC cells contain PD-L1. If your TNBC cells have the PD-L1 protein, you may respond well to pembrolizumab. Pembrolizumab is known as a PD-1 inhibitor, or an immune checkpoint inhibitor. If a PD-1 protein on a T cell attaches to a cancer cell with high amounts of PD-L1, the T cell turns off and won’t attack the cancer cell. Pembrolizumab can block PD-1 and prevent T cells from being switched off, allowing T cells to attack breast cancer cells.
Pembrolizumab may be given alongside other TNBC treatment options, including chemotherapy (chemo) and breast cancer surgery. Chemotherapy drugs for TNBC that are sometimes given with pembrolizumab include:
Read more about chemotherapy for TNBC.
Pembrolizumab is FDA-approved to treat early and advanced TNBC alongside chemo in the following cases:
Pembrolizumab is considered a first-line treatment option for people with advanced TNBC who test positive for the biomarker PD-L1.
Pembrolizumab is given as an IV infusion (into a vein) every three weeks or six weeks. Your doctor will recommend a dosing schedule based on your specific needs.
Both of the approved immunotherapies for TNBC have been shown to extend survival.
Clinical trials found that adding pembrolizumab to chemo in people with TNBC can help them live longer compared to receiving chemo alone. TNBC is an aggressive type of breast cancer — it usually grows and spreads quickly and has a high risk of recurrence (when cancer comes back) compared to other types of breast cancer.
A clinical trial compared chemo with pembrolizumab for advanced TNBC versus chemo with a placebo, or inactive treatment. Researchers measured the participants’ median overall survival — the length of time from diagnosis that half of the clinical trial participants are still alive. The median overall survival for the group that received pembrolizumab plus chemotherapy was 23 months, compared to 16 months for the placebo-plus-chemo group.
In people with early TNBC, adding pembrolizumab to neoadjuvant chemotherapy increased the chance of a complete response to the treatment. A complete response refers to when no cancer is found in the breast or lymph nodes.
If you have locally advanced or metastatic TNBC and tried two other earlier lines of treatment, your doctor may recommend another type of immunotherapy known as an antibody-drug conjugate. Sacituzumab govitecan-hziy contains a monoclonal antibody that targets and binds to a protein called trophoblast cell-surface antigen 2 (TROP2) on cancer cells. It then delivers a drug into the cell that causes its death. The drug is indicated to treat advanced or metastatic TNBC if surgery isn’t an option and at least two other therapies have been tried.
In clinical trials, participants who received sacituzumab lived a median of three months longer without disease progression — and a median of five months longer altogether — than those given chemotherapy. Sacituzumab shrank tumors in 35 percent of people without metastasis (breast cancer spread) in the brain, compared with 5 percent of those who received chemotherapy.
Like all drugs, even those sold over the counter, immunotherapy can cause side effects. The side effects of TNBC treatment can vary from person to person.
Possible side effects of pembrolizumab include:
Pembrolizumab affects your immune system. This may cause serious or life-threatening side effects, such as an infusion or autoimmune reaction.
An infusion reaction can happen while the drug is being administered into your bloodstream. Symptoms include:
An autoimmune reaction can occur if your immune system makes antibodies (special immune system proteins) that attack healthy parts of your body, such as your lungs, intestines, liver, or kidneys. Autoimmune reactions can happen because pembrolizumab removes one of the safeguards that your immune system uses to help prevent these attacks.
In clinical trials, the most common side effects of sacituzumab were low white blood cell counts, nausea, and diarrhea. This medication may also cause:
It can also cause serious infusion reactions.
Immunotherapy for breast cancer is a new area of study in cancer research. Researchers are pursuing new treatments for breast cancer and TNBC.
Several clinical trials studying immunotherapy for TNBC are underway. Some clinical trials are investigating new ways of using existing immunotherapy drugs. For example, researchers are exploring the safety and effectiveness of pembrolizumab alone, not combined chemotherapy. New immunotherapy treatments for TNBC may include other immune checkpoint inhibitors or new categories of medication.
New forms of immunotherapy are under development to fight triple-negative breast cancer. You may be eligible to participate in research.
Cancer vaccines are another type of immunotherapy under development that may be available in the future. A cancer vaccine may be able to produce an immune response that activates immune cells to attack breast cancer cells.
If you have TNBC, talk to your cancer care team to find out if immunotherapy can help improve your outcome. They can help determine if your TNBC is among the 1 in 5 cases that have PD-L1 protein, the biomarker that predicts a good response to pembrolizumab treatment. In addition, you can talk to your cancer care team to find out if you qualify for any clinical trials that are testing possible new TNBC treatments.
MyBCTeam is the social network for people with breast cancer and their loved ones. On MyBCTeam, more than 67,000 members come together to ask questions, give advice, and share their stories with others who understand life with breast cancer.
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Madison Saxton, PharmD
obtained her Doctor of Pharmacy from Lake Erie College of Osteopathic Medicine (LECOM) in Bradenton, Florida.
Learn more about her here.
Amanda Jacot, PharmD
earned a Bachelor of Science in biology from the University of Texas at Austin in 2009 and a Doctor of Pharmacy from the University of Texas College of Pharmacy in 2014.
Learn more about her here.
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