Breast Cancer

What Is Metastatic Breast Cancer? Symptoms, Causes, Treatments, and More

Julie Lynn Marks
By
Lisa D. Curcio, MD, FACS
by
Updated on May 16, 2024
Metastatic breast cancer is the term for breast cancer that has spread to other areas of the body, and is the most advanced stage of the disease. Doctors may also refer to it as stage 4 breast cancer.

In metastasis, cancer cells break away from the original tumor and travel to other organs. Cancer cells can spread by moving through your bloodstream or lymphatic system (the network of lymph nodes and vessels in your body).

In the case of metastatic breast cancer, cancer cells most commonly spread from the breast to the bones, brain, liver, and lungs, according to Breastcancer.org.

 Even when the cancer spreads to a different organ, it’s still named after its original location. For example, doctors may find cancer in your lungs, but if the cancer started in your breast, it’s considered metastatic breast cancer (not lung cancer).
While there’s currently no cure for metastatic breast cancer, treatment may be helpful in slowing cancer growth, improving disease symptoms, and extending survival, according to the American Cancer Society (ACS).

Types of Metastatic Breast Cancer

There are two types of metastatic breast cancer, per the Cleveland Clinic:

  • De novo This means the cancer has already spread to another area of the body at the time of diagnosis. About 6 percent of women in the United States are initially diagnosed with metastatic breast cancer, per the American Society of Clinical Oncology (ASCO).

  • Distant recurrence This refers to breast cancer that was not considered metastatic at the time of diagnosis, but has come back in another area of the body after treatment. A distant recurrence is more common than a de novo metastatic breast cancer diagnosis.

What Are the Signs and Symptoms of Metastatic Breast Cancer?

The signs and symptoms of metastatic breast cancer depend on the area of the body that the cancer has affected and how far the cancer has spread, according to the Breast Cancer Research Foundation. Some general problems that could signal disease metastasis include fatigue, poor appetite, and unexplained weight loss.

illustrative graphic titled, how metastatic breast cancer affects the body. woman centered surrounded by symptoms including speech or vision problems, shortness of breath,, belly pain, itchy skin, fatigue, weight loss, bone pain, jaundice, nausea

Metastatic breast cancer can cause any or all these symptoms, depending on where the cancer has spread.

Everyday Health

Symptoms of breast cancer that has spread to the bones include:

  • Bones are easily broken or fractured
  • Bone pain
  • Swelling

Symptoms of breast cancer that has spread to the brain include:

  • Changes in behavior
  • Issues with memory
  • Nausea or vomiting
  • Persistent headaches 
  • Seizures
  • Speech or vision issues

Symptoms of breast cancer that has spread to the liver include:

  • Abdominal pain
  • Jaundice (yellowing of the skin or whites of the eyes)
  • Nausea or vomiting
  • Rash or itchy skin
  • High liver enzymes in the blood

Symptoms of breast cancer that has spread to the lungs include:

  • Pain in the chest
  • Persistent cough
  • Shortness of breath

What Causes Metastatic Breast Cancer?

Most of the time, breast cancer metastasizes because, for some, initial treatments haven’t completely destroyed all the cancer cells, or because some cancer cells have already spread but were too few in number to be detected. The remaining cancer cells are weakened and their numbers are reduced, so they may be undetectable on tests for a time. Eventually, they can strengthen and can spread to parts of the body outside the breast, according to the Cleveland Clinic.

How Is Metastatic Breast Cancer Diagnosed?

To diagnose metastatic breast cancer, your doctor may perform some of the following tests, per ASCO. Not all tests will be used for every person:

  • Biopsy A tumor biopsy involves removing a small portion of tissue from the bone, liver, lungs, lymph nodes, or other part of the body, and sending it to a pathologist (a specialist who looks for diseases in tissue and fluid samples). It is the most definitive way to test for cancer cells, per ASCO.

  • Computed tomography (CT) scan A CT scan may be used to detect tumors or other abnormalities in the bone, liver, lung, or lymph nodes. This type of scan can also measure the size of tumors. 
  • Magnetic resonance imaging (MRI) This test produces images of the inside of your body and is also able to determine a tumor’s size.
  • Positron emission tomography (PET) scan A sugar tracer containing a small amount of radioactive substance is injected into your vein. This substance will collect in cells that have higher levels of activity, like cancer cells. A scanner then shows where the radioactive substance has been absorbed. A PET scan is often combined with a CT scan (PET-CT scan) when checking to see if breast cancer has spread.
  • Bone scan Your doctor may perform this test to see if cancer has spread to your bones.
  • X-ray This may be used to check if breast cancer has spread to the lungs.
  • Blood tumor marker tests This type of blood test is performed to find tumor proteins, also called serum tumor markers, in your blood. However, these proteins are also found in people with other conditions that are not cancer. Therefore, this is not considered a diagnostic test.
  • Complete blood count (CBC) This may be done to measure the number of different types of blood cells you have and determine whether or not your bone marrow is working properly. 
  • Serum chemistry blood tests This test measures the minerals in your blood and looks for abnormal enzymes, which may be a sign that cancer has spread away from the breast. Abnormal test results are commonly found for many other conditions that are not cancer, so this is not a diagnostic test. It may also determine how well your kidneys and liver are functioning. 

Testing a Metastatic Tumor

Once a diagnosis of metastatic breast cancer is confirmed, your doctor may perform more tests to identify the traits of the tumor, discovering your breast cancer subtype. This information is important for determining which treatment options will be most successful.

Your doctor may test for:

  • Hormone receptor status If a tumor tests positive for either estrogen receptors (ER) or progesterone receptors (PR), it’s called hormone receptor (HR)–positive. When estrogen or progesterone bind to these receptors on breast cancer cells, they stimulate cell growth. Hormone therapies work by either blocking the hormones from binding to the receptor or decreasing estrogen levels in the body.

  • HER2 status Human epidermal growth factor receptor 2 (HER2) is a protein that helps cancer cells grow at a quicker pace. If a cancer is HER2-positive, doctors may recommend treatments that specifically target the HER2 protein. If breast cancer expresses a very small amount of HER2, it’s considered HER2-low and may be treated similarly to breast cancers that have no HER2 (called HER2-negative), according to the National Cancer Institute.

Breast cancers that have all three receptors (ER, PR, and HER2) are called triple-positive breast cancers. Breast cancers that do not have any estrogen receptors, progesterone receptors, or HER2 are referred to as triple-negative breast cancers. These types of cancers typically grow at a faster rate compared to HR-positive and HER2-positive breast cancers, per the ACS.

Breast Cancer Subtype
ER/PR
HER2
HR-Positive/HER2-Negative
ER+, PR+, or both
–
HR-Positive/HER2-Positive (Triple-Positive)
ER+ and PR+
+
HR-Negative/HER2-Positive
ER– and PR–
+
HR-Negative/HER2-Negative (Triple-Negative)
ER– and PR–
–
You may have gotten some of these tests done following an earlier breast cancer diagnosis, but your doctor may recommend repeating the tests because a breast cancer’s hormone receptor or HER2 status can change after metastasis.

 But usually, the metastasized cancer has similar characteristics as the original breast cancer.

Additionally, your doctor may want to conduct genetic testing.

 Genetic testing looks for specific gene mutations you may have inherited from your parents, such as BRCA1 and BRCA2, and helps identify treatment options based on this information.

Treatment Options for Metastatic Breast Cancer

Treatment options for metastatic breast cancer will depend on a variety of factors:

  • Where the cancer has spread in your body
  • The tumor’s hormone receptor and HER2 status
  • The tumor’s gene mutations
  • Your symptoms
  • Treatments you’ve received in the past
  • Overall health
While treatment for metastatic breast cancer is not expected to cure the disease, it can extend survival and improve quality of life.

Hormone Therapy

Metastatic breast cancers that are HR-positive use the estrogen and progesterone hormones in your body to aid in the growth and spread of cancer cells. Hormone therapy is usually the first treatment option for this type of metastatic breast cancer. Depending on its form, hormone therapy works by either lowering levels of these hormones in your body or blocking them from reaching cancer cells. It may be used in combination with targeted therapies.

There are many hormone therapies available. Doctors commonly recommend:

  • Tamoxifen This medication is an estrogen receptor blocker, which works by preventing estrogen from binding to cancer cells. 
  • Aromatase inhibitors (AIs) AIs work by blocking the aromatase enzyme, causing the tissues in your body to decrease estrogen production. This treatment is used in women who have already undergone menopause or in premenopausal women along with ovarian suppression.
  • Ovarian suppression This treatment is used in women who have not yet undergone menopause. It involves either surgery or medication to stop the ovaries from making estrogen, putting the woman into menopause.

These treatments are often used in combination with a type of targeted drug called CDK 4/6 inhibitors, which work by blocking the proteins responsible for cell division. Stopping cell division slows tumor growth. CDK 4/6 inhibitors include: 

Sometimes, breast cancer cells don’t respond to the hormone therapies above, or some patients may have unacceptable side effects. In those cases, your oncologist may try what’s called “second-line” treatments:

  • fulvestrant (Faslodex) This treatment is commonly used when an HR-positive/HER2-negative metastatic breast cancer doesn’t respond to hormone therapy and continues to grow. Fulvestrant works by preventing estrogen from attaching to estrogen receptors. 
  • elacestrant (Orserdu) This drug is used for women with an estrogen receptor mutation who have already been treated with but didn’t respond to hormone therapy. Elacestrant can also be used to treat men with advanced breast cancer.

Chemotherapy

Chemotherapy involves using drugs to kill cancer cells. Most of the time, chemotherapy drugs are given one at a time for advanced cancer, instead of in combination with each other, but may be used alongside other forms of treatment, according to the ACS.

Some chemo medications that may be used to treat metastatic breast cancer include:

Targeted Therapy

Targeted therapies can be directed at (target) specific genes or proteins on breast cancer cells that help them grow and spread. Targeted therapies work by either blocking certain proteins or by delivering a chemo drug directly to cancer cells.

There are several types of targeted therapies, and the type of targeted therapy your doctor recommends will depend on your tumor’s biology.

CDK 4/6 inhibitors are a targeted drug used in combination with hormone therapy to treat HR-positive breast cancers, as described above in the Hormone Therapy section.

Other targeted therapies used to treat metastatic HR-positive, HER2-negative (or HER2-low) breast cancer include the following:

  • Alpelisib (Piqray) is given with the hormone therapy fulvestrant to people who have HR-positive breast cancer with a PIK3CA gene mutation.
  • Capivasertib (Truqap) is given with fulvestrant for HR-positive breast cancer with one or more mutations in the PIK3CA, AKT1, or PTEN genes.
  • Everolimus (Afinitor) blocks the mTOR protein (a protein that helps cells grow and divide), and is given with the AI exemestane for HR-positive breast cancer that didn’t respond to a previous AI.

Targeted therapies used to treat metastatic HER2-positive breast cancer include:

A type of targeted therapy called PARP inhibitors destroy cancer cells by preventing them from fixing damage to their cells. These drugs are used to treat metastatic HER2-negative breast cancer in patients with certain gene mutations such as BRCA1 and BRCA2, and include:

For HER2-low metastatic breast cancer, trastuzumab deruxtecan (Enhertu) may be used. 

And for people with metastatic triple-negative breast cancer, or for people with HR-positive, HER2-negative breast cancer whose disease progressed after hormone therapy and two chemotherapy drugs, sacituzumab govitecan (Trodelvy) may be an option.

Immunotherapy

Immunotherapy involves using the body’s own immune system to fight cancer. The following immunotherapies may be used to treat metastatic breast cancer.

Radiation

Radiation involves using high-energy X-rays or other particles to kill cancer cells. The treatment may help shrink tumors or improve symptoms. It may also be used for breast cancer that has spread to the brain or bones.

Surgery

Surgery isn’t commonly used to treat metastatic breast cancer, but it can be an option in certain cases. For example, doctors may perform surgery to help prevent blockage in the liver caused by cancer cells, avoid broken bones, or manage pain and other symptoms.

Clinical Trials

Clinical trials are research studies that look for new ways to treat or prevent different diseases. People with metastatic breast cancer may benefit from participating in a clinical trial by receiving certain therapies that aren’t available otherwise. Talk to your doctor about the pros and cons of joining a clinical trial.

Risk Factors for Metastatic Breast Cancer

Any form of breast cancer can spread, and experts are not currently able to predict when metastasis will happen, but there are a few factors that may contribute to your risk of developing metastatic breast cancer, including:

  • Breast cancer subtypes HER2-positive and triple-negative breast cancers are more aggressive and tend to have higher rates of metastasis compared with HR-positive cancers, according to one 2020 study.

  • How the cancer grows Fast-growing cancers are more apt to metastasize.
  • The stage at diagnosis A breast cancer’s stage describes how much the disease has spread, with a higher stage indicating more spread.

What Is the Prognosis of Metastatic Breast Cancer?

The outlook for people with metastatic breast cancer varies. It’s estimated that a third of women in the United States who are diagnosed with metastatic breast cancer live at least five years after their diagnosis, according to Cleveland Clinic, though each individual will have different outcomes that may be influenced by breast cancer type, form of treatment, and overall health, among other factors.

Prevention of Metastatic Breast Cancer

There’s no surefire way to stop breast cancer from metastasizing, but research suggests that hormone therapy, such as tamoxifen, may help to lower the risk of breast cancer recurrence in both pre- and postmenopausal women. Hormone therapy works by preventing estrogen activity, which breast cancer relies on to grow, helping to slow the growth of tumors in the breast.

You may be able to lessen the chances of a metastatic breast cancer diagnosis if your cancer is caught early. Routine mammograms can help doctors find cancers sooner.

You can also reduce your risk of developing breast cancer by:

  • Maintaining a healthy weight
  • Being physically active
  • Avoiding alcohol, or drinking in moderation
  • Breastfeeding if you have children
If you are currently taking hormone replacement therapy or oral birth control, consider talking to your doctor about the risks associated with these medications. And if you have a family history of breast cancer, or think you might have the BRCA1 or BRCA2 gene mutations, talk to your doctor about considering genetic testing and other ways you can lower your risk.

Research and Statistics: Who Has Metastatic Breast Cancer?

It’s estimated that 200,000 women are living with metastatic breast cancer in the United States, according to the Breast Cancer Research Foundation, who also notes that, in recent years, there’s been an increase in metastatic breast cancer cases among young women.


Metastatic breast cancer can also affect men, but male breast cancer is rare. Less than 1 percent of all breast cancers occur in men, according to Breastcancer.org.

 In 2023, it was estimated that nearly 2,800 men developed breast cancer, and about 530 men died of the disease, per the ACS.

Black Americans and Metastatic Breast Cancer

Although breast cancer is more common in white women, data published by the ACS suggests that Black women are diagnosed with breast cancer that has already reached a later stage, including stage 4, more often than white women.

Black women are also more likely to have breast cancer at a younger age and have a 40 percent higher death rate than their white counterparts, per the ACS.

 Black women under the age of 50 in particular are twice as likely to die from the disease as white women of the same age. 
Researchers are conducting studies to better understand why this disparity exists. According to the Breast Cancer Research Foundation, some possible reasons include:

  • Social and economic factors, such as culture, poverty, and social injustice

  • Unequal access to medical care
  • Biological differences in breast tumors, such as a greater proportion of triple-negative breast cancers — a more aggressive breast cancer — in Black women

  • Lifestyle habits, including higher alcohol consumption, poor diet, and smoking

Black men with breast cancer also tend to have a worse prognosis, the ACS notes.

Related Conditions and Causes of Metastatic Breast Cancer

Some conditions closely related to metastatic breast cancer include:

  • Breast cancer Breast cancer begins when a malignant tumor grows in breast tissue.
  • Ductal carcinoma in situ (DCIS) DCIS originates in the milk ducts of the breast and makes up about 1 in 5 new breast cancer cases.
  • Invasive ductal carcinoma (IDC) IDC is the most common type of breast cancer. It also begins in the milk ducts, but ultimately spreads outside the ducts and into fatty tissue in the breast.  
  • Invasive lobular carcinoma (ILC) ILC begins to grow in the lobules, or the milk-producing glands, of the breast, and makes up about 1 in 10 cases of invasive breast cancer (cancer that spreads to fatty tissue). 
  • Inflammatory breast cancer (IBC) With IBC, lymph vessels are blocked by cancer cells, which may result in redness or swelling of the breast. IBC accounts for up to 5 percent of all breast cancer cases.

  • Triple-negative breast cancer (TNBC) TNBC describes breast cancer that doesn’t have any estrogen or progesterone receptors, or HER2 proteins. Up to 15 percent of breast cancers are triple-negative.

Editorial Sources and Fact-Checking

Everyday Health follows strict sourcing guidelines to ensure the accuracy of its content, outlined in our editorial policy. We use only trustworthy sources, including peer-reviewed studies, board-certified medical experts, patients with lived experience, and information from top institutions.

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