Targeted therapies for hormone-receptor positive breast cancer

Hormoneinfo-icon-receptorinfo-icon positive breast cancers grow in response to the hormones estrogeninfo-icon and progesteroneinfo-icon. These cancers are often treated with hormonal therapyinfo-icon medicines. 

Hormonal therapy medicines can work in two ways. They either stop the body from making estrogen or they block the effects of estrogen that drive cancer growth.

Over time, some breast cancers build resistance to hormonal therapies. If this happens, your doctor may then suggest a different medicineinfo-icon. The new medicine might be a targeted therapyinfo-icon. Studies have shown that some hormonal therapies are more effective when combined with certain targeted therapies.

Targeted therapies are treatments that target specific proteins or markers on or within cancer cells that help cancer cells grow. There are many different kinds of targeted therapy. Hormonal therapy is a type of targeted therapy because it targets hormones that are active in cancer growth. Hormonal therapy has been used to treat breast cancer for many years. Doctors now use other new kinds of targeted therapy to treat hormone receptorinfo-icon-positive breast cancer as well.

The FDAinfo-icon has approved three new kinds of targeted therapy to treat hormone receptor-positive breast cancer – mTORinfo-icon inhibitors, CDK 4/6 inhibitors, and PI3K inhibitors. These medicines are mostly used to treat metastaticinfo-icon breast cancers. Only one CDK 4/6 inhibitor is also approved for early-stage breast cancerinfo-icon.

If you have hormone receptor-positive breast cancer and are interested in targeted therapies, ask your doctor whether these medicines are an option for you. If they are not, ask if you might be able to participate in a clinical trialinfo-icon.

In this section, you’ll learn more about the classes of targeted therapies used to treat hormone receptor-positive breast cancer and the medicines within each type.

Targeted therapies often have fewer side effects than chemotherapyinfo-icon, but like any medicine, they may still cause them. Medicines that target features of cancer cells that are also in healthy cells can cause more side effects. Side effects vary in type and level of seriousness. What you experience depends on how your body responds to the medicine.

Your doctor, pharmacistinfo-icon, or nurseinfo-icon can help you manage any side effects. Visit our Side Effects page for more information on common side effects and how to copeinfo-icon with them.

CDK 4/6 inhibitors

CDK 4/6 inhibitors, also called cyclin-dependent kinase 4/6 inhibitors, target two specific kinases, CDK 4 and 6. These kinases, or proteins, signal cancer cells to grow and divide. This type of medicineinfo-icon slows the growth or spread of cancer cells. Three CDK 4/6 inhibitors are approved to treat metastaticinfo-icon breast cancer. Of the three, only abemaciclib is also approved for early-stage breast cancerinfo-icon. The three CDK 4/6 inhibitors are:

mTOR inhibitors

mTORinfo-icon, or mammalian target of rapamycin, is a type of proteininfo-icon called a kinase. Kinase helps control cellinfo-icon growth.

In some cancers, mTOR-activated proteins work abnormally and encourage cancer cells to grow and spread. mTOR also directs nutrients to the cancer cells, helping to support them.

mTOR inhibitors are a newer type of targeted therapyinfo-icon. They work to slow or stop mTOR’s role in the growth of cancer cells. The mTOR inhibitor approved to treat metastaticinfo-icon breast cancer is:

PI3K inhibitors

PI3K, also called phosphatidylinositol-3 kinase, is a family of enzymes that sends signals that affect cell growth. One medicine of this kind is approved to treat hormone receptor-positive, HER2-negative metastatic breast cancer that has a specific mutation, PIK3CA, in postmenopausal women and in men:

Updated 
July 25, 2022