Metastatic breast cancer, also called stage IV breast cancer, occurs when breast cancer has spread from the breast to distant parts of the body. It is considered advanced breast cancer and can affect organs such as the bones, liver, lungs, or brain. Although metastatic breast cancer is generally not considered curable, modern treatments can often control the disease, relieve symptoms, and help many people live longer with a good quality of life.
Breast cancer becomes metastatic when cancer cells travel through the bloodstream or lymphatic system and establish tumors in distant organs.
Metastatic disease may be diagnosed when breast cancer is first discovered, but it can also develop months or years after treatment for an earlier-stage breast cancer.
The characteristics of the original tumor, including hormone receptor and HER2 status, remain important when selecting treatment.
Symptoms depend on where the cancer has spread.
Possible symptoms include:
Some people with metastatic breast cancer have few symptoms, particularly early in the course of metastatic disease.
Metastatic breast cancer can spread to almost any organ, but certain locations are more common.
Bone metastases may cause persistent pain and can weaken bones, increasing the risk of fractures.
Liver metastases may cause abdominal discomfort, fatigue, appetite changes, or abnormal liver-function tests. Extensive involvement can eventually interfere with liver function.
Cancer that spreads to the lungs can cause coughing, shortness of breath, chest discomfort, or fluid around the lungs.
Brain metastases can cause headaches, seizures, balance problems, weakness, vision changes, or changes in memory and behavior.
Diagnosis usually involves a combination of clinical evaluation, imaging, and laboratory testing.
Possible tests include:
A biopsy can help confirm that a suspicious lesion represents metastatic breast cancer.
Importantly, doctors may repeat testing for estrogen receptor, progesterone receptor, and HER2 status because tumor characteristics can change between the original breast cancer and metastatic disease.
Treatment for metastatic breast cancer depends heavily on its biological subtype.
Many breast cancers contain estrogen receptors, progesterone receptors, or both.
Hormone therapy is often a major part of treatment. It may be combined with targeted medicines such as CDK4/6 inhibitors in appropriate patients.
HER2-positive cancers produce excess HER2 protein.
Several HER2-targeted therapies are available, including antibody-based treatments and antibody-drug conjugates. Treatment selection depends on previous therapies and the specific clinical situation.
Triple-negative breast cancer does not have estrogen receptors, progesterone receptors, or excess HER2.
Treatment can involve chemotherapy, immunotherapy for selected patients, antibody-drug conjugates, and other targeted approaches when specific molecular characteristics are present.
There is no single treatment that works for every person with metastatic breast cancer.
For hormone receptor-positive disease, endocrine therapy can slow cancer growth by blocking hormonal signaling.
Depending on the situation, treatment may include aromatase inhibitors, selective estrogen receptor modulators, selective estrogen receptor degraders, or ovarian-function suppression.
Targeted therapies are designed to interfere with specific molecular pathways involved in cancer growth.
Examples include CDK4/6 inhibitors for many hormone receptor-positive cancers and HER2-directed therapies for HER2-positive disease.
Chemotherapy may be used for different metastatic breast cancer subtypes.
It can be particularly important when cancer is growing rapidly, causing significant symptoms, or when hormone-based or targeted treatments are not appropriate or have stopped working.
Immunotherapy may be used for selected patients, particularly some people with metastatic triple-negative breast cancer.
Biomarker testing can help determine whether an immune checkpoint inhibitor may be appropriate.
Antibody-drug conjugates combine a cancer-targeting antibody with a potent drug.
They are designed to deliver treatment more directly to cancer cells and have become an increasingly important part of metastatic breast cancer treatment.
When breast cancer spreads to the brain, treatment depends on the number, size, location, symptoms, and overall disease status.
Possible treatments include:
The treatment plan is often developed by a multidisciplinary team.
Bone-directed treatments can help reduce complications associated with bone metastases.
Depending on the situation, doctors may use medicines such as bisphosphonates or denosumab.
Radiation therapy can also help relieve pain from specific bone lesions.
Regular dental evaluation may be recommended before and during certain bone-strengthening treatments because of the uncommon risk of jaw complications.
Supportive care is an important component of metastatic cancer treatment.
Management may include:
Palliative care can be provided alongside cancer treatment. It focuses on symptom management, quality of life, and support for patients and families.
Metastatic breast cancer is generally treated as a chronic condition requiring ongoing monitoring and treatment adjustments.
Doctors may use imaging, physical examinations, laboratory tests, and symptom assessments to determine whether treatment is controlling the cancer.
If a treatment stops working or causes unacceptable side effects, another treatment may be considered.
Advances in targeted therapies, antibody-drug conjugates, immunotherapy, and molecular testing continue to expand treatment possibilities.
Prognosis varies considerably among people with metastatic breast cancer.
Factors that can influence outlook include:
Some people live for many years with metastatic breast cancer because modern treatments can control the disease for extended periods.
Metastatic breast cancer is stage IV breast cancer that has spread beyond the breast and nearby lymph nodes to distant organs. Common sites include the bones, liver, lungs, and brain. Although metastatic breast cancer is generally not considered curable, it can often be treated for long periods, and the main goals are to control cancer growth, reduce symptoms, prevent complications, extend survival, and maintain quality of life.
Diagnosis usually involves imaging and, when appropriate, a biopsy of a suspicious metastatic area. Testing the tumor for estrogen receptors, progesterone receptors, and HER2 is especially important because these characteristics strongly influence treatment. Additional molecular testing may identify mutations or biomarkers that make specific targeted therapies appropriate.