Medications Used for Triple-Negative Breast Cancer

Breast cancer treatment is unique for everyone. It often includes a combination of surgery, radiation, and medications. Many treatments target certain proteins found on cancer cells. But triple-negative breast cancer is different — these proteins are missing or not often found.

Triple-negative breast cancer (TNBC) is a more aggressive type of breast cancer. It makes up about 10% to 15% of all breast cancers. Since TNBC cells don’t have the same proteins that other breast cancer treatments target, it’s more difficult to treat. But other treatments are available for TNBC.

Read on to learn more about TNBC and the medications that treat it.

What is triple-negative breast cancer?

Receptors (chemical binding sites) are proteins that bind to certain substances in your body. There are three main receptor types found on breast cancer cells. Breast cancer medications usually target these receptors if they’re present.

1. Estrogen receptors: Estrogen is a hormone that can make breast cancer grow. It acts as a fuel source. Estrogen in the body can attach to estrogen receptors on cancer cells and help the cancer grow. Some breast cancer cells have estrogen receptors. These are called “ER-positive” cancers (ER+).

2. Progesterone receptors: Progesterone is another hormone that can fuel cancer growth. Progesterone in the body can attach to progesterone receptors on cancer cells and help the cancer grow. If cancer cells have progesterone receptors, it’s called “PR-positive” cancer (PR+). 

3. HER2: HER2 is a protein on the outside of cells that can make breast cancer grow and spread faster. When breast cancer cells have more HER2 than normal, they’re called “HER2-positive” cancers (HER2+). 

TNBC is when breast cancer cells don’t have estrogen or progesterone receptors and don’t make HER2. Because these proteins aren’t on cancer cells, your cancer specialist may sometimes call it ER-/PR-/HER2- breast cancer. 

Who is most at risk for triple-negative breast cancer?

TNBC tends to be more common in women under 40 years old. It’s also more common in African American women.

People who have a mutation (change) in a gene called BRCA1 also have a higher TNBC risk. BRCA genes (BRCA1, BRCA2) help repair DNA in our cells. If this gene is mutated, cells can’t fix broken DNA. This can lead to breast cancer. 

What’s more, up to 72% of women who have a BRCA1 mutation will develop breast cancer by 70 to 80 years old.

Why is triple-negative breast cancer more difficult to treat?

Other types of breast cancer are usually treated with hormone therapy or targeted therapy. Hormone therapy works by targeting estrogen or progesterone receptors in HR+ cancers. Targeted therapy works against HER2 proteins in HER2+ cancers. 

TNBC can be difficult to treat because cancer cells don’t have the usual treatment targets described above. And it can be more aggressive, growing and spreading faster than other types of breast cancer. In fact, TNBC is more likely to come back after treatment, typically within the first 5 years after diagnosis.

What medications are used to treat triple-negative breast cancer?

TNBC treatment is different for every person. Treatment depends on many factors, including:

• Tumor (cancer) size 

• If the cancer has spread (metastasized) to other parts of your body

• Biopsy (tissue sample) results

• Other general health issues

Surgery is an option if a tumor is small enough. Radiation is a treatment that kills cancer cells by using energy. It may be added if a tumor is large or if nearby tissues have cancer cells. 

Medications can be used alone or in combination with surgery or radiation. Some treatments used in other breast cancers won’t work for TNBC. But there are a few medications that are used — alone or in combination — to fight TNBC.

Remember: Cancer is complex. You may need to try several different treatments before you find one that works for you.

So, always ask your cancer specialist questions! It’s important to know and consider your treatment options, along with their risks.

Chemotherapy

Chemotherapy is a main medication option for TNBC. This is because it works broadly in your body and doesn’t target specific proteins. There are many types of chemotherapy medications used to treat TNBC. 

Chemotherapy works by damaging the DNA in cancer cells. It’s a common anti-cancer medication used to shrink tumors, and it can be given before and after surgery. It may also be given with other medications, like an immunotherapy medication (mentioned below). 

Below are examples of chemotherapy options for TNBC. Most medications are given as an infusion into your vein or as an injection.

• Alkylators: These damage cancer cell DNA to stop them from growing. Examples include carboplatin (Paraplatin) and cisplatin (Platinol).

• Microtubule inhibitors: These stop cells from dividing to prevent tumors from growing. Examples include paclitaxel (Taxol), docetaxel (Taxotere), and vinorelbine (Navelbine).

• Anthracyclines: These prevent DNA from multiplying, thus stopping the cancer cell from growing. Examples include doxorubicin (Adriamycin) and epirubicin (Ellence).

• Antimetabolites: These interfere with how cancer cells grow and divide by affecting its DNA. Examples include capecitabine (Xeloda) and gemcitabine (Gemzar). 

Chemotherapy medications can be given by themselves, but they’re often given in combination with other ones. A combination of two or more chemotherapies make up a chemotherapy regimen. Another article describes how chemotherapy regimens and acronyms work, but a few examples are listed below:

• AC → T: Doxorubicin and cyclophosphamide followed by paclitaxel or docetaxel

• TC: Docetaxel and cyclophosphamide

• EC: Epirubicin and cyclophosphamide

• TAC: Docetaxel, doxorubicin, and cyclophosphamide

This isn’t a comprehensive list of breast cancer chemotherapy medications. To learn more, click or tap here. 

Chemotherapy side effects

As mentioned, chemotherapy can attack cancer cells. But it can also attack other fast-growing healthy cells in your body. This includes hair follicles and cells in your digestive tract. Because of this, you may experience some side effects with treatment. 

Side effects vary depending on the medications you’re receiving, but a few common ones include:

• Hair loss

• Nail changes

• Mouth sores

• Loss of appetite

• Tiredness

• Weight changes

• Nausea, vomiting, constipation, or diarrhea

Chemotherapy can also affect different cells in your body. This can cause low red blood cells, white blood cells, or platelets (blood cells involved in clotting). 

Immunotherapy

Your immune system helps your body fight infections from germs like bacteria and viruses. It also helps your body fight cancer. Immunotherapy medications work by helping your immune system more effectively fight cancer cells.

Immune checkpoint inhibitors (blockers) are a type of immunotherapy. Immune checkpoints are parts of the immune system, and they act as a form of protection. They can help prevent an immune response from being too strong. An immune response that’s too strong could potentially damage healthy cells. 

Immune checkpoint inhibitors help bolster your immune system by turning these protections “off.” This causes your immune system to ramp up and attack cancer cells. 

If TNBC is caught early, an immune checkpoint inhibitor can be used with chemotherapy before surgery and then alone after surgery. It can also be used in combination with chemotherapy for advanced (metastatic) TNBC. 

Examples include pembrolizumab (Keytruda) and atezolizumab (Tecentriq) — both are available as intravenous (IV) infusions. Pembrolizumab is used for early and advanced TNBC, and atezolizumab is used for advanced TNBC. Common side effects include rash, diarrhea, and feeling tired.

Targeted therapies

Targeted therapies are different from chemotherapy and immunotherapy. They don’t damage cancer cells like chemotherapy does. They also don’t affect the immune system like immunotherapy does.

Targeted therapies work by affecting genetic mutations (changes). They don’t affect normal cells. There are two types of targeted therapies often used for TNBC — PARP inhibitors and antibody-drug conjugates.

PARP Inhibitors

PARP inhibitors work by blocking an enzyme (protein) called PARP. PARP inhibitors prevent cancer cells from repairing their DNA. BRCA gene mutations make it hard for DNA to properly repair itself, so PARP inhibitors are used in breast cancers with BRCA mutations. They help make cancer cells die by preventing them from fixing their DNA. 

Genetic testing is done on breast cancer tissue to see if the cells have a BRCA gene mutation.

Examples of PARP inhibitors include olaparib (Lynparza) and talazoparib (Talzenna). They’re used in people who’ve already had chemotherapy. Olaparib is an oral tablet that can be used in metastatic breast cancer. Talazoparib is an oral capsule that’s approved for use in locally advanced and metastatic breast cancers. Locally advanced cancer is cancer that has started to spread to nearby areas, but that hasn’t spread to other parts of the body.

Common side effects of PARP inhibitors include: 

• Nausea and vomiting

• Diarrhea

• Tiredness

• Loss of appetite

• Changes in taste

• Muscle and joint pain

Like chemotherapy, PARP inhibitors can affect different cells in your body. In rare cases, some people have developed blood cancer.

Antibody-drug conjugates

Antibody-drug conjugates (ADCs) are therapies that combine two medications together — monoclonal antibodies and chemotherapy. Chemotherapies are mentioned above, but monoclonal antibodies are proteins that target and attach to specific substances in your body. Think of a monoclonal antibody as a delivery vehicle that delivers chemotherapy directly to cancer cells.

Sacituzumab govitecan (Trodelvy) is an ADC used in metastatic TNBC. It’s a monoclonal antibody (sacituzumab) linked to govitecan, a type of chemotherapy. Sacituzumab attaches to a protein on cancer cells called Trop-2. When this happens, govitecan can enter the cancer cell and damage it. 

Govitecan has many of the same chemotherapy side effects listed above. Sacituzumab can cause side effects like nausea, diarrhea, and fatigue. It can also cause a type of allergic reaction during infusion. Allergy medications are given before treatment to help prevent these reactions.

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Written by:

Emmeline C. Academia, PharmD, BCOP

Emmeline C. Academia, PharmD, BCOP, has been a practicing clinical pharmacist in adult oncology since 2020. She is a clinical pharmacy specialist in oncology at Beth Israel Deaconess Medical Center, in Boston.

Edited by:

Alyssa Billingsley, PharmD

Alyssa Billingsley, PharmD, is the director of pharmacy content for GoodRx. She has over a decade of experience as a pharmacist and has worked in clinical, academic, and administrative roles.

Reviewed by:

Joshua Murdock, PharmD, BCBBS

Joshua Murdock, PharmD, BCBBS, is a licensed pharmacist in Arizona, Colorado, and Rhode Island. He has worked in the pharmacy industry for more than 10 years and currently serves as a pharmacy editor for GoodRx.

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