Metastatic Breast Cancer: A Guide to Diagnosis and Treatment Options

Around 6% to 10% of people with breast cancer have metastatic disease at the time of their initial diagnosis. This means the cancerous cells from the original tumor have traveled to other parts of the body and formed additional tumors. In breast cancer, tumors most commonly develop in the liver, lungs, brain, and bones. 

If you or someone you care about has been diagnosed with metastatic breast cancer, it can feel frightening and confusing, to say the least. We’ll walk you through exactly what this diagnosis means and how it is treated, so you can better understand what to expect. 

What is metastatic breast cancer?

Metastatic cancer is the most advanced stage of breast cancer — also called “stage 4.” Staging a cancer accounts for many factors. But the presence of metastasis automatically categorizes a cancer as stage 4. Breast cancer will typically first spread to nearby lymph nodes, which are small organs that are part of the immune system. The cancer is not considered metastatic until it has spread beyond the lymph nodes to more distant parts of the body.

Breast cancer can travel through the body by two different paths: the bloodstream or the lymphatic system. The cancer cells that start in the breast use these pathways like transportation highways to other organs, where they can create new tumors. Even when a new tumor develops in a different organ (often referred to as a “met”), it’s still considered breast cancer.  

What are the types of metastatic breast cancer?

There are many different types of breast cancer. And many of them are categorized by the area of the breast where they first start. A “ductal carcinoma” is one of the most common types, and it’s a cancer that arises from milk duct tissue in the breast. Other types of breast cancer can start in the “lobules” of the breast (invasive lobular carcinoma) or even the skin and lymph cells (inflammatory breast cancer).

But even within one type of breast cancer, the cells in a tumor can have different properties. The presence or absence of certain receptors on cancer cells is another important way that breast cancer is categorized. 

There are two main types of breast cancer receptors:

• Hormone receptors: Cancer cells with receptors for estrogen and progesterone on their surface are known as estrogen receptor-positive (ER+) and progesterone receptor-positive (PR+).

• Human epidermal growth factor receptor 2 (HER2): HER2 is a protein on the surface of breast cells that’s responsible for cell growth. Breast cancer cells with an increased amount of HER2 on their surface are known as HER2 positive (HER2+). 

Breast cancer cells may have any combination of ER, PR, and HER2. Triple-negative breast cancer refers to breast cancer that doesn’t contain any hormone receptors or high amounts of HER2. 

The receptor status is important because it helps predict the aggressiveness of a cancer. It also helps determine the treatment options that will work best for that particular cancer.

Symptoms of metastatic breast cancer

The symptoms of metastatic breast cancer vary based on the location of the metastases. Sometimes there may be no symptoms. But in many cases, the first symptoms are related to where the cancer has spread. 

Bone metastases

Bones are the most common site of breast cancer metastases. Almost 54% of people who have metastatic breast cancer have bone involvement. Some of the symptoms of bone mets include:

• Bone pain

• Weaker bones that are more prone to fracture

The breakdown of bone from metastasis can also lead to high calcium levels — also called hypercalcemia. Hypercalcemia symptoms include confusion or mood changes, abdominal pain, constipation, and body aches. 

Bone mets can also affect the bone marrow’s production of blood cells and can lead to anemia (decreased blood counts). Anemia symptoms can include fatigue (tiredness), lack of energy or shortness of breath with light activity, easy bruising, and feeling cold all the time.

Lung metastases

Up to 32% of people with metastatic breast cancer will develop lung metastases at some point in the course of their disease. Most people with lung metastases don’t have any symptoms initially. But if symptoms are present, the most common ones are: 

• Shortness of breath

• Chest pain

• Cough, sometimes with blood-streaked mucus

Brain metastases

The brain is a common site of spread in breast cancer, especially in people who have HER2-positive or triple-negative metastatic breast cancer. Up to 32% of people with these breast cancer subtypes will develop brain metastases. The symptoms of brain metastasis can include:

• Persistent headaches

• Nausea and vomiting

• Seizures

• Changes in vision

• Personality changes  

Liver metastases

Around 3% to 8% of people with metastatic breast cancer will have liver mets at the time of their initial diagnosis. Most people won’t have any initial symptoms from liver metastases. But if the liver metastases progress, people may experience: 

• Abdominal pain

• Swelling of the abdomen from an accumulation of fluid (known as ascites)

• Yellowing of the skin

• Nausea and vomiting

Diagnosis of metastatic breast cancer

A diagnosis of metastatic breast cancer can be discovered in many different ways. It often depends on an individual’s unique case and symptoms. Sometimes, a stage 4 diagnosis starts with an abnormality found on mammography. In other cases, a metastasis is found before the primary breast cancer. This is particularly true when a metastatic tumor is causing symptoms that prompted the initial workup. Imaging studies, like CT scans, MRIs, or X-rays, may show metastases to various parts of the body. 

There may be differences in how the diagnostic workup starts. But most people will have a biopsy of one of the tumors. In addition to a biopsy, a team of healthcare providers, including a cancer specialist (oncologist), will usually order blood tests, perform a physical exam, and sometimes order more imaging studies to assess the degree and location of cancer spread.

Treatment of metastatic breast cancer

Metastatic breast cancer is not curable, but there are still effective treatments for it. And it’s important to remember that the goals of treatment are different for each person. Goals may include focusing on treating the symptoms or shrinking the tumors to increase life expectancy as much as possible. Another goal may be to avoid unwanted side effects by minimizing treatments like chemotherapy.

Every person and every situation is different. It’s important to consider what’s most important to you when discussing treatment options with your oncologist. Some people want to take the most aggressive treatment approach possible. Others prefer to prioritize symptom management. Either way, you have many options. And there are several treatment strategies available for metastatic breast cancer.

Systemic therapy

Systemic therapy is the mainstay of treatment in metastatic breast cancer. Systemic therapy is the most effective treatment for metastatic disease because the medication is delivered to the whole body — and all the different areas of cancer — at the same time. This involves taking medication either orally or intravenously (IV). 

The goal of systemic therapy is to kill the cancer cells and shrink the tumors. This may help to decrease the symptoms or increase life expectancy in some cases. 

There are four main types of systemic therapy: 

1. Chemotherapy helps to destroy rapidly dividing cancer cells. It’s often given as an IV infusion. There are many side effects because chemotherapy will also kill some normal cells. These commonly include hair loss, nausea, weakness, fatigue, anemia, and weakened immune system. Chemotherapy is often given at a lower dose in metastatic cancer. The lower doses make it easier to receive the treatment over a longer period of time. 

2. Targeted therapy refers to medications that specifically target HER2-positive breast cancer. There are many different types of medications in this category. And they come in different forms. Some can be taken orally, while others are given through an IV or an injection. 

3. Hormone therapy, also known as endocrine therapy, may help people who have hormone receptor-positive (ER+ or PR+) breast cancer. These medications are usually taken orally, though some may be injected into the skin. Hormone therapy blocks the receptors on the cancer cells, thus slowing their growth. These are often combined with targeted therapies, which makes them even more effective.

4. Immunotherapy helps the body use its immune system to target and kill cancer cells. This type of systemic treatment is less common because not all breast cancers will respond to this type of treatment. These medications are usually given as an IV infusion, like in chemotherapy. Immunotherapy can sometimes cause immune cells to attack normal cells in the body, and lead to side effects that resemble an autoimmune condition.

Locoregional therapy 

Locoregional therapy includes surgery and radiation. This differs from systemic therapy because it targets cancer in one area or location. It’s used less often in metastatic breast cancer because it isn’t an effective way to address all of the areas of tumor spread. 

It may be helpful in some cases to help with tumors that are causing significant symptoms. This is especially true when breast cancer has spread to the brain because it’s harder for chemotherapy to reach these areas. Radiation is used more often than surgery as a treatment for metastatic tumors.

Symptom management

An important part of any treatment plan is to ease someone’s symptoms. There are many options to help with pain caused by a tumor or treatment side effects such as nausea and vomiting. So your healthcare provider can help, it’s important to tell them about any symptoms you’re experiencing. 

Treatment can also include medications to help with some of the mental health challenges — such as depression or anxiety — that come with metastatic breast cancer. And there are many ways to address these feelings and symptoms beyond medication.

Living with a diagnosis of metastatic breast cancer

Treatment for metastatic breast cancer involves more than just treating the disease. It’s about providing emotional support for people with breast cancer and their loved ones. Finding the right support for your mental health can be a powerful way to be in control of your experience while living with a difficult diagnosis. It may help to remember that:

• It’s OK to focus on your experience and symptoms rather than aggressive treatment. And prioritizing your quality of life can have a powerful effect on survival. Many people with metastatic breast cancer live for several years with this diagnosis.

• It can be tempting to compare your case and experience to the experiences of others. But remember that everyone is different. And the way someone chooses to treat and live with metastatic breast cancer can look very different from person to person. 

• It’s important to surround yourself with people who support you. This includes friends, family, a counselor or therapist, a support group, and your cancer specialists. 

• While it’s easier said than done, be patient with yourself. Processing your emotions and reflecting on your treatment goals can take some time. 

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Written by:

Joanna Jan, MD

Joanna Jan, MD, is board-certified in internal medicine and licensed to practice medicine in the state of Pennsylvania. In 2017, she received her board certification from the American Board of Internal Medicine.

Edited by:

Katie E. Golden, MD

Katie E. Golden, MD, is a board-certified emergency medicine physician and a medical editor at GoodRx.

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