If you recently received a diagnosis of metastatic breast cancer (MBC), it’s natural to wonder what treatments are out there and what they can do for you. There’s no cure for MBC, also called stage 4 breast cancer, but it’s treatable. Researchers have developed new treatments that continue to improve life expectancy and prevent the further spread or worsening of metastatic disease, extending progression-free survival for people living with metastatic breast cancer.

Knowing more about treatments can help you have better conversations with your doctor about your options. You’ll work with your cancer care team to come up with a treatment plan that balances fighting cancer with improving quality of life and limiting side effects. Read on to learn more about new MBC treatments, including research on how they extend life and help people with MBC feel their best.

Chemotherapy

Chemotherapy has been used for decades to treat several types of cancer, including MBC. Chemotherapy drugs work by interfering with cell growth and division in rapidly dividing cells (such as cancer cells). Until the 1960s, cancer treatments mainly focused on surgery and radiation therapy — however, researchers learned that chemotherapy could better control disease, helping improve survival rates.

Over the years, doctors and researchers have found that some chemotherapy drugs are especially effective for treating MBC. These drugs include:

• 5-fluorouracil (5-FU)
• Capecitabine (Xeloda)
• Cyclophosphamide
• Docetaxel (Taxotere)
• Doxorubicin
• Methotrexate
• Paclitaxel protein-bound (Abraxane)

Studies show that chemotherapy has reduced the risk of death by 7 percent to 33 percent in people with invasive or metastatic breast cancer, according to PLOS One. Today, chemotherapy is often combined with targeted therapies, which aim at different proteins or hormones to make them more effective at treating MBC.

Hormone Therapy

As researchers learned more about breast cancer, they found that some cells rely on hormones like estrogen or progesterone to grow. These hormones bind to receptors on the outside of tumor cells, telling them to grow and divide rapidly. Your doctor may classify your MBC as estrogen receptor (ER)-positive or progesterone receptor (PR)-positive if you have these receptors on your breast cancer cells.

With this discovery, researchers developed targeted therapies to block these receptors and effectively stop breast cancer cells from growing. In 1977, the U.S. Food and Drug Administration (FDA) approved tamoxifen, the first anti-estrogen drug for treating breast cancer. More than 50 percent of people with hormone receptor-positive (HR-positive) breast cancer who take tamoxifen see their cancer stabilize, according to Wolters Kluwer UpToDate. However, others don’t respond to the medication at all.

These drugs, called aromatase inhibitors, reduce estrogen in the body, and they’ve proved effective in treating ER-positive metastatic breast cancers. This class of drugs includes:

• Anastrozole (Arimidex)
• Letrozole (Femara)
• Exemestane (Aromasin)

Another hormone therapy, fulvestrant (Faslodex), was approved in 2002 for treating hormone-sensitive breast cancer. In 2017, the FDA expanded the drug’s approval to include postmenopausal treatment of HR-positive metastatic breast cancer.

Per the National Cancer Institute, one study showed that fulvestrant stopped MBC progression for 16.6 months, compared to only 13.8 months with the drug anastrozole. This means that fulvestrant helped people live longer with stable disease compared to anastrozole.

New Therapies for Advanced HR-Positive Breast Cancer

Capivasertib combined with fulvestrant (Truqap) was approved for HR-positive, HER2-negative breast cancer in 2023. Capivasertib is a serine/threonine kinase inhibitor. The combination drug may be recommended for people whose breast cancer cells have certain mutations and who’ve already tried other treatments.

Sacituzumab govitecan-hziy (Trodelvy) was also approved for HR-positive, HER2-negative breast cancer in 2023. This treatment may be recommended for people whose breast cancer has progressed despite trying other therapies. Trodelvy is an antibody-drug conjugate that targets cancer cells with specific mutations and kills them with an anti-cancer drug.

HER2 Therapies

In some cases, breast cancer cells produce too much of a protein called HER2. Previously, people with HER2-positive MBC were treated with chemotherapy. A clinical trial comparing trastuzumab (Herceptin) to standard chemotherapy found that trastuzumab helped to better stabilize participants’ disease. On average, people who received trastuzumab lived longer than those given chemotherapy. The FDA approved Herceptin in 1998.

Some cancer therapies work better combined with others than they do on their own. In 2012, the FDA approved the HER2 drug pertuzumab (Perjeta) for use with trastuzumab and chemotherapy in people with HER2-positive MBC. A study published in The New England Journal of Medicine showed that this combination helped people live nearly 16 months longer than trastuzumab and chemotherapy alone.

In 2022, the FDA approved fam-trastuzumab deruxtecan-nxki (Enhertu) as the first treatment for people who have MBC with low levels of HER2. Fam-trastuzumab delivers chemotherapy directly to cancer cells. Studies showed that it stabilized disease more, according to the FDA, helping people live nearly seven months longer than chemotherapy alone.

Tyrosine Kinase Inhibitors

Tyrosine kinases are specialized proteins that send signals for cancer cells to grow and divide. Breast cancer cells can make too many of these proteins and then grow out of control. Medications known as tyrosine kinase inhibitors (TKIs) block this uncontrolled cell growth.

The first TKI approved by the FDA for treating HER2-positive MBC was lapatinib (Tykerb), in combination with capecitabine, in 2007.

In 2020, the FDA approved two more TKIs — neratinib (Nerlynx) and tucatinib (Tukysa). Clinical trials found that both drugs stopped cancer progression longer than the currently available therapies did, helping people live longer.

Cyclin-Dependent Kinase 4/6 Inhibitors

Cyclin-dependent kinase (CDK) 4/6 inhibitors, another fairly new class of medications, block the enzymes CDK4 and CDK6. These drugs interfere with breast cancer cell division, stopping cells from replicating. In 2015, based on clinical trial results, the FDA began approving CDK4/6 inhibitors to treat HER2-negative MBC, including:

• Palbociclib (Ibrance) — Palbociclib prevented cancer progression for 10 months longer compared to control treatment, according to the FDA.
• Abemaciclib (Verzenio) — Abemaciclib prevented cancer progression for seven months longer than the control treatment, per the FDA.
• Ribociclib (Kisqali) — Seventy percent of people taking ribociclib were alive after 42 months, compared to 46 percent of people taking hormone therapy alone, according to the National Cancer Institute.

PI3 Kinase Inhibitors

Phosphoinositide 3-kinase (PI3K) inhibitors can be used to treat cancers with the PIK3CA gene mutation. Alpelisib (Piqray) is now FDA-approved.

PARP Inhibitors

Some breast cancers are caused by mutations in the BRCA1 and BRCA2 genes, which normally help repair damaged DNA. Researchers have developed new medications specifically to treat people with HER2-negative MBC with BRCA1 and 2 mutations. These drugs are known as poly (ADP-ribose) polymerase (PARP) inhibitors.

In 2018, the FDA approved the PARP inhibitors olaparib (Lynparza) and talazoparib (Talzenna) for treating people with MBC who’d already undergone chemotherapy. Both medications were shown to prevent cancer from progressing longer than chemotherapy, helping participants live longer with stable disease.

Checkpoint Inhibitors

Some breast cancer cells have a protein known as PD-L1 on their surface that helps them hide from the immune system. Checkpoint inhibitors are a type of immunotherapy that blocks PD-L1, allowing your immune system to recognize cancer.

In 2020, the FDA approved pembrolizumab (Keytruda) with chemotherapy to treat metastatic triple-negative breast cancer that’s positive for PD-L1. This combo was shown to nearly double the time to cancer progression compared to treatment with a placebo (“fake” drug) and chemotherapy, according to the FDA.

Promising Treatments for Metastatic Breast Cancer

As they learn more about MBC, doctors and researchers look for new ways to treat it. Sometimes they develop new drugs that target breast cancer in a novel way, while other studies focus on finding ways to repurpose currently available therapies.

New treatments being studied in laboratories or in clinical trials in people with MBC include:

• Medications that block androgen receptors (similar to ER and PR) to slow breast cancer cell growth
• Medications that block CDK7 to interrupt cancer cell division
• New types of PARP inhibitors, antibody-drug conjugates, and antiestrogen therapies

If you’re interested in learning more about new treatments for MBC, talk to your oncologist. Clinical trials are an option for those looking to try an experimental therapy that may be beneficial.

You may also be curious about how eating a nutritious diet can help you feel your best while treating MBC. Your doctor can suggest the best eating plan for you along with other ways to practice good self-care while living with metastatic breast cancer.

Talk With Others Who Understand

MyBCTeam is the social network for people with breast cancer and their loved ones. On MyBCTeam, more than 68,000 members come together to ask questions, give advice, and share their stories with others who understand life with breast cancer.

Are you living with metastatic breast cancer? Have you talked with your doctor about new treatment options? Share your experience in the comments below, or start a conversation by posting on your Activities page.