Metastatic breast cancer (MBC), also called stage IV breast cancer, occurs when cancer cells from the breast spread to distant organs. These may include the bones, liver, lungs, or brain. Metastatic disease is not considered curable, but it is treatable. Many patients live for years with ongoing therapy and careful monitoring.
Breast cancer becomes metastatic when cancer cells travel through the blood or lymphatic system and form new tumors elsewhere. This process can happen months or years after early-stage breast cancer treatment, or it may be present at the first diagnosis.
This article explains metastatic breast cancer in clear terms, covering causes, symptoms, diagnosis, treatment options, prognosis, and unique clinical considerations.
What Is Metastatic Breast Cancer?
Metastatic breast cancer means that breast cancer cells have spread beyond the breast and nearby lymph nodes to distant organs. It is classified as stage IV, regardless of tumor size.
The most common metastatic sites are:
- Bones
- Liver
- Lungs
- Brain
Less commonly, cancer may spread to the skin, distant lymph nodes, or bone marrow.
How Breast Cancer Spreads
Cancer spreads through several steps:
- Cancer cells break away from the primary breast tumor.
- They enter blood vessels or lymphatic channels.
- Cells travel to other parts of the body.
- They settle and grow in new tissues.
Even when cancer spreads, it is still called breast cancer based on the original tumor type, not the organ it reaches.
Common Symptoms of Metastatic Breast Cancer
Symptoms vary depending on where cancer has spread. Some patients have no symptoms at first.
General Symptoms
- Ongoing fatigue
- Unintentional weight loss
- Loss of appetite
- Persistent pain
Bone Metastases
- Bone pain, often in the back or hips
- Increased risk of fractures
- High calcium levels in blood
Lung Metastases
- Shortness of breath
- Chronic cough
- Chest pain
Liver Metastases
- Abdominal swelling or pain
- Jaundice
- Abnormal liver blood tests
Brain Metastases
- Headaches
- Vision problems
- Seizures
- Changes in balance or behavior
Diagnosis of Metastatic Breast Cancer
Diagnosis usually involves imaging, lab tests, and sometimes biopsy.
Imaging Tests
- CT scans
- PET scans
- Bone scans
- MRI of brain or spine
Blood Tests
- Liver function tests
- Calcium levels
- Tumor markers (used cautiously)
Biopsy
A biopsy of a metastatic site may be done to:
- Confirm cancer type
- Recheck hormone receptor status
- Identify HER2 status changes
Types of Metastatic Breast Cancer
Treatment decisions depend on cancer biology.
Hormone Receptor–Positive (HR+)
- Estrogen receptor (ER) or progesterone receptor (PR) positive
- Often slower growing
- Responsive to hormone therapy
HER2-Positive
- Overexpression of HER2 protein
- Treated with targeted anti-HER2 drugs
Triple-Negative Breast Cancer (TNBC)
- Lacks ER, PR, and HER2
- More aggressive
- Limited targeted options
Treatment Options for Metastatic Breast Cancer
Treatment aims to:
- Control cancer growth
- Reduce symptoms
- Improve quality of life
- Prolong survival
Systemic Therapies
Hormone Therapy
Used for HR-positive disease:
- Aromatase inhibitors
- Tamoxifen
- Fulvestrant
Often combined with targeted drugs.
Targeted Therapy
- CDK4/6 inhibitors
- HER2-targeted agents
- PI3K or mTOR inhibitors (selected cases)
Chemotherapy
Used when:
- Cancer is aggressive
- Hormone therapy no longer works
- Rapid disease control is needed
Immunotherapy
Used in selected triple-negative cases with specific biomarkers.
Local Treatments
Radiation Therapy
- Pain relief
- Control of brain or bone metastases
Surgery
Rarely used, but may help in specific situations.
Living With Metastatic Breast Cancer
MBC is often treated as a chronic illness. Ongoing care includes:
- Regular scans
- Treatment adjustments
- Symptom management
- Emotional and social support
Palliative care is recommended early to improve comfort and daily function.
Prognosis and Survival
Survival varies widely. Factors affecting prognosis include:
- Cancer subtype
- Sites of metastasis
- Response to treatment
- Overall health
Many patients now live longer due to advances in targeted therapy. Median survival has improved over the past two decades, though individual outcomes differ.
Unique Clinical Takeaways
1. Receptor Status Can Change Over Time
Hormone receptor or HER2 status may differ between the original tumor and metastatic sites. Re-biopsy can change treatment plans and improve response.
2. Symptom Burden Does Not Always Match Disease Extent
Some patients with widespread disease feel well, while others with limited spread have severe symptoms. Treatment decisions should prioritize patient-reported outcomes, not imaging alone.
3. Bone Health Requires Active Management
Bone metastases increase fracture risk. Early use of bone-modifying agents, calcium monitoring, and fall prevention strategies can reduce complications.
4. Treatment Sequencing Matters
Using less toxic therapies first can preserve quality of life without reducing survival. Aggressive treatment is not always the best initial choice.
5. Psychosocial Support Impacts Clinical Outcomes
Depression, anxiety, and financial stress affect adherence and symptom control. Integrated mental health care improves overall disease management.
Ongoing Research and Clinical Trials
Research areas include:
- New targeted drugs
- Antibody-drug conjugates
- Personalized therapy based on genetic testing
- Better symptom control strategies
Clinical trials may offer access to new treatments and should be discussed with oncology teams.
Medical Disclaimer
This content is for informational purposes only and does not replace professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider regarding medical conditions or treatment decisions