Understanding Your Diagnosis

Metastatic Breast Cancer (MBC)

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Learning that breast cancer has spread can be overwhelming and heartbreaking. Metastatic breast cancer (MBC) is serious, and while it is not curable, it is treatable—often for many years with the help of newer medicines. This FAQ is designed to give you clear, gentle explanations during a time that may feel especially heavy.

Frequently Asked Questions About MBC

What does it mean when breast cancer is metastatic?

Where can breast cancer spread when it becomes metastatic?

Is breast cancer in nearby lymph nodes considered metastatic?

How MBC Is Diagnosed

Learning you may have metastatic breast cancer can feel overwhelming, especially when symptoms or test results appear unexpectedly. This checklist walks you through the types of evaluations your care team may use so you know what to expect, and can feel more grounded and informed throughout the process.

Medical History and Physical Exam

A full review of any new symptoms you’re experiencing, as these can sometimes hint at where the cancer may have spread. For example, unexplained shortness of breath may be a sign that cancer has spread to the lung.

Imaging Tests to Locate and Track Metastasis

Your team may use one or more imaging tools to evaluate the spread of disease, including:

CT scan
Ultrasound
MRI
PET scan
Bone scan

These scans help show where cancer is present and how extensive it may be.

Biopsy of the Metastatic Site

A tissue biopsy may be taken from the area where cancer is suspected (such as the bone, liver, or lymph node).
The biopsy:

Confirms the diagnosis of metastatic breast cancer

Provides updated information about your tumor’s stage, grade, and receptor status. Read more about this in Breast Cancer 101.

Watch Receptor Status

Recheck the receptors whenever MBC is found. Receptor status can change between your original breast cancer and a metastatic diagnosis. It can also change over the course of living with MBC.

Blood Tests for Tumor Markers

Your team may check levels of blood proteins such as CEA or CA 15-3. These markers:

Can be elevated in MBC

Help monitor disease along with imaging and symptoms

Should not be used alone to make treatment decisions

Why Breast Cancer Sometimes Spreads

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MBC happens when breast cancer cells break away from the original tumor and grow in other parts of the body; often the lungs, bones, liver, or brain. For most people, there’s no clear reason why their cancer spreads. Here’s what we do know:

Even years after treatment for early-stage breast cancer, the cancer can return in a new place. Up to one-third of patients develop MBC despite our best efforts to treat the initial cancer.
About 5–10% of people discover metastatic disease at their very first breast cancer diagnosis. This is called de novo MBC.
Triple negative breast cancers (those without estrogen, progesterone, or HER2 receptors) have a higher chance of spreading within the first 3 years after diagnosis.
Hormone-receptor–positive breast cancers (ER/PR-positive) can return as metastatic disease many years after the original diagnosis.

Treatment of MBC

When you’re living with metastatic breast cancer, treatment focuses on helping you feel as well as possible while slowing or stopping the cancer from spreading. Most treatment is given as medicines that travel throughout your body—your care team may call this systemic therapy—and many people benefit from different combinations over time.

Systemic Treatment

Here are the main types your team may recommend:

Chemotherapy: Chemotherapy uses medicines that kill fast-growing cancer cells or stop them from growing. Learn more about chemotherapy.
Endocrine Therapy: If your cancer is hormone-receptor positive, endocrine therapy works by blocking the hormones that help the cancer grow. Learn more about endocrine therapy.
HER2 Directed Therapy: If your cancer is HER2-receptor there are many types of therapies that directly target HER2, including antibodies, small molecule inhibitors, and antibody-drug conjugates. Learn more about HER2 directed therapy.
Other Targeted Therapy: These medicines focus directly on specific proteins within breast cancer cells that help them grow, spread, or survive. They can destroy cancer cells or slow their growth. Learn more about targeted therapies.
Immunotherapy: These treatments help strengthen your body’s own immune system so it can better recognize and attack cancer cells. Learn more about immunotherapy.

Throughout treatment, your care team will work closely with you to find the options that best match your cancer’s characteristics and your personal goals so you can move forward with clarity, support, and hope.

Other Potential MBC Treatments

Radiation

Radiation therapy uses high-energy particles to kill or damage cancer cells, and it can be an important tool for managing symptoms in MBC. Your team may consider radiation for several reasons:

Pain relief: to reduce discomfort from bone metastases.
Symptom control: to address bleeding or symptoms caused by tumors affecting the brain or spinal cord.
Brain metastases: whole-brain radiation therapy (WBRT) or stereotactic radiosurgery (SRS) is often used when breast cancer spreads to the brain.

Learn more about radiation therapy.

Surgery

For metastatic breast cancer, surgery is not considered a primary treatment. Studies have shown that removing the original breast tumor does not improve outcomes or extend life for people with MBC, and in some cases, it may even be harmful.

However, your care team may recommend surgery in specific situations—to ease symptoms such as pain or bleeding—when doing so can restore comfort or improve your quality of life.