• Metastatic breast cancer (MBC) is stage 4 of breast cancer progression, not a separate type of breast cancer.
• Stage 4 means breast cancer has spread to areas outside the breast tissue.
• Some women have MBC when they are first diagnosed, but most cases represent a recurrence of earlier-stage cancer that was previously treated.
• MBC is not curable, but it is treatable.

The way we speak and think about breast cancer is often focused on early detection and aggressive treatment. We’re taught that catching cancer early makes a cure more likely. When someone is undergoing breast cancer treatment, we assume the goal is a cure, and then treatment will end.

That model doesn’t describe metastatic breast cancer, which is the stage when breast cancer spreads to other organs. In fact, MBC (also known as stage 4 breast cancer) is incurable, but it is treatable. Treatment for MBC may last for many years or be lifelong. Living with MBC is often very different from living with earlier stages of breast cancer.

In 2023, 297,790 women were newly diagnosed with breast cancer. The Young Survival Coalition has found that between 20 percent and 30 percent of women diagnosed with early-stage breast cancer will eventually progress to stage 4. MBC has long been poorly understood. As we learn more about MBC and more women share their experiences, there’s a growing understanding of stage 4 breast cancer and better support for women who are living with it.

In this article, we will explore common areas of the body where MBC tends to spread, how it’s treated, and what this diagnosis means for you.

What Is Metastatic Breast Cancer?

Breast cancer develops in the breast tissue, but breast cancer cells can spread to other parts of the body through the lymphatic system and blood vessels. The process of cancer cells spreading outside the breast is known as metastasis. When breast cancer cells or tumors are found in other parts of the body, they are known as metastases. Breast cancer that has spread in this way is referred to as metastatic, or stage 4, cancer.

There are different types and subtypes of breast cancer. Some types of breast cancer are more aggressive and invasive than others.

Between 5 percent and 9 percent of women are diagnosed with MBC when they are first diagnosed with breast cancer, according to the Young Survival Coalition. De novo MBC refers to breast cancer that is initially diagnosed as stage 4 or MBC without any prior history of being detected at an earlier stage. More often, MBC is a recurrence of a previous breast cancer diagnosis. This is also known as a distant recurrence.

Common Sites of Breast Cancer Metastases

Breast cancer metastases are breast cancer cells that spread and grow in parts of the body outside of the breasts and immediate surrounding tissue. A common misconception is that because MBC occurs in, for example, the brain, it is brain cancer. Actually, the cancer cells remain breast cancer cells regardless of where they grow in the body.

Different types of cancer tend to metastasize in certain body parts or tissues. Breast cancer can spread anywhere in the body, but it tends to affect certain organs more than others. MBC most commonly metastasizes to the bones, liver, brain, and lungs. MBC can sometimes affect reproductive and sex organs and the gastrointestinal tract.

Bones

Bone metastasis is the most common location for MBC. More than half of all women with MBC have bone metastases that predominantly affect arm and leg bones and the spine, ribs, and pelvis. The most common symptom women reported was new bone pain.

Lungs

Lung metastasis can be asymptomatic for long periods of time, meaning it doesn’t show symptoms. When it does, symptoms can include shortness of breath, persistent dry cough, and pain with breathing.

Brain

According to Breastcancer.org, brain metastasis occurs in 10 percent to 15 percent of women with MBC. Symptoms of brain metastases depend on where in the brain they occur and which neurological functions are affected. They can include pain, memory problems, and vision or speech changes.

Liver

Liver metastases don’t usually cause a great deal of noticeable symptoms. When symptoms are present, they may include jaundice, pain, and fatigue.

How Is Metastatic Breast Cancer Diagnosed?

Often, MBC is discovered because of the symptoms it causes. Pain is a common symptom that accompanies breast cancer metastasis in all regions of the body. Specifically, pain associated with MBC is new or sudden pain that is noticeable, fairly severe, and tends to recur. Sometimes, MBC doesn’t have any noticeable symptoms and is detected during other routine scans or tests.

When MBC is suspected, several imaging tests, labs, and other procedures are conducted to accurately diagnose the potential metastases, locate tumors, and assess the extent of metastasis. The following tests are used to investigate and diagnose MBC:

• MRI can identify spinal tumors or brain metastases.
• Blood tests check blood chemistry and blood cell counts for abnormalities and imbalances. Sometimes, cancer biomarkers may be helpful as well.
• Bone scans (or bone scintigraphy) capture images and possible irregularities of the bones.
• Positron-emission tomography (PET) scans capture images of the body’s cells at work.
• CT scans use X-rays to capture cross-sectional images of organs.
• Chest X-rays can determine whether cancer has spread to the lungs.

Test results can also serve as a baseline to measure how a person’s cancer is responding to a treatment or to check disease progression.

What Is the Prognosis for Metastatic Breast Cancer?

After a cancer diagnosis, most people want concrete information. They ask questions like “How long?” or “How likely?” Sometimes, doctors don’t have an answer. “I ask [my oncologist] all the time, ‘Am I going to live?’ but he won't answer,” explained one MyBCTeam member living with MBC. “I eventually decided that I do not want this answer. Not today.”

Calculating an individual’s MBC prognosis is complex. Survival rate statistics don’t always reflect new and experimental treatments. The prognosis for MBC varies greatly from person to person and cancer to cancer. MBC prognosis depends on many factors specific to the person, as well as the type of MBC they have.

Cancer Characteristics

Doctors use several data points about an individual’s breast cancer to develop a treatment plan and figure out the prognosis. This information may include:

• The type and subtype of breast cancer
• Characteristics such as hormone receptor status, genetic details, and HER2 status
• How aggressive the cancer or cell-growth rate is
• Which organs are affected and how widely the breast cancer has metastasized
• Whether a breast cancer’s biology changes or metastases develop resistance to treatment

Personal Characteristics

Many personal characteristics can affect MBC prognosis. Age plays a role in MBC progression and recurrence. Risk of breast cancer increases with age. Hormonal factors during and after menopause may also play a role. Your genetic makeup can also affect how breast cancer behaves in your body.

The longer a person survives with MBC, the longer they’re likely to continue to live with MBC. This concept is known as conditional survival.

The stark reality is that the prognosis for MBC is not as good as the prognosis for other breast cancer stages. About one-third of women survive at least five years after their initial MBC diagnosis, according to Susan G. Komen. MBC’s progression can also be unpredictable. Some people live 10 or more years with MBC.

MBC will almost always mean a shorter life expectancy than for those without MBC. Almost certainly, MBC will require being on treatment and under close medical monitoring for the rest of one’s life. A diagnosis of MBC is not a death sentence, and it is not the end.

How Is Metastatic Breast Cancer Treated?

The treatment philosophy behind MBC management is very different from other cancer stages. Stage 4 cancer treatment aims to manage symptoms, extend life expectancy, and preserve a person’s quality of life. The potential benefit of each treatment is heavily weighed against potential negative outcomes.

Systemic therapy like hormonal therapy and immunotherapy, treatments like radiation and surgery, and targeted therapies are all options for treating MBC. Chemotherapy drugs are also often a part of MBC treatment. While it can be effective in destroying cancer cells, chemotherapy can cause severe side effects and have a detrimental impact on a person’s quality of life. All treatments for MBC carry potential risks, as well as potential benefits. When determining the best approach for managing MBC, medical professionals and the people they treat must weigh the potential risks and benefits of available treatments.

Treating MBC differs greatly from other breast cancer treatment in that there is no finish line. Managing MBC entails continual, lifelong treatment. Some people live with MBC as a chronic condition for years. Essentially, people with MBC continue a specific treatment until it no longer works. In consultation with their breast cancer treatment team, they will then move on to the next best MBC treatment options. Some MBC treatments may be new or experimental.

Be sure to speak with your doctor about clinical trials to see if they may be appropriate for your MBC treatment plan.

Support for People Living With Metastatic Breast Cancer

Living with MBC can be a heavy emotional burden, especially on bad days. In addition to your health care team, social support is an important part of living well with MBC. One MyBCTeam member shared, “I can handle the physical stuff, the almost-weekly chemo, but I’m having trouble dealing with it all mentally. I’m angry, sad, frustrated. … Does anyone else have some good coping skills?”

Although thousands of people live with MBC in the United States, life with MBC can feel very lonely. Those who are younger may have an especially difficult time coping with the challenges — physical, mental, emotional, and social. Connecting with others who understand the day-to-day issues of living with stage 4 breast cancer can improve your mood and help lessen feelings of isolation. Talk to your patient navigator about local support resources, or join online cancer support communities like MyBCTeam.

Some people with advanced-stage cancer experience depression. Chemotherapy, hormonal therapy, and some medications can make depression worse. If feelings of anxiety, sadness, or anger last longer than a few weeks or disrupt your day-to-day life, you should speak to your doctor about support and treatment options.

Find Your Team

On MyBCTeam, the social network for people with breast cancer and their loved ones, more than 67,000 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? Has support from MyBCTeam helped you through a difficult time? Share your experiences in the comments below, or start a conversation by posting on your Activities page.