What is Metastatic Breast Cancer?

Metastatic breast cancer is the most advanced stage of breast cancer (stage 4) and happens when the cancer spreads to other areas of the body. More specifically, metastatic cancer is when the cancer cells break away from the original tumor and move to different organs in the body. The cancer cells travel through your body by way of the bloodstream and lymphatic system. The most common areas of the body metastatic breast cancer spreads to are the bones, brain, liver, and lungs. Regardless of the organ it spreads to, the cancer will always be referred to as breast cancer because that was its origin.

Breast cancer occurs when abnormal cells of the breast begin to divide uncontrollably. A tumor is a mass that is formed from a collection of abnormal cells. Although a cure does not exist for breast cancer, many advancements in research and development of better treatments have increased survival rate and quality of life.

There are two main types of metastatic breast cancer, which include:

• De novo metastatic breast cancer. This occurs when metastatic breast cancer is the first diagnosis of breast cancer.
• Distant recurrence. This happens when breast cancer recurs after treatment of the original breast cancer, and it spreads to other areas of the body. Sometimes this can occur years after the original breast cancer diagnosis and treatment.

Signs and Symptoms

The early signs and symptoms of metastatic breast cancer depend on what parts of the body and what type of tissue the cancer cells have invaded. The most common areas of the body breast cancer spread to are the bones, brain, liver, and lungs.

Bone metastases symptoms:

• Bone pain
• Bone fractures
• Swelling

Brain metastases symptoms:

• Persistent and progressively worsening headaches or pressure in the head
• Seizures
• Visual disturbances or changes in vision
• Personality or behavioral changes
• Loss of balance
• Issues with speech or memory

Liver metastases symptoms:

• Jaundice
• Rash or itchy skin
• Stomach issues (pain, loss of appetite, nausea, or vomiting)
• Abnormally high liver enzymes

Lung metastases symptoms:

• Lingering cough
• Chest pain
• Difficulty breathing or catching your breath

Other symptoms of metastatic breast cancer may include fatigue, unexplained weight loss, or poor appetite. Additionally, metastatic breast cancer may be suspected if a liver test reveals high enzymes or if a chest x-ray shows signs of a problem. Please consult with your healthcare professional if you notice any of these symptoms.

Causes

Metastatic breast cancer usually occurs when the initial treatments for the original breast cancer did not destroy all the cancer cells. There is a period where the cancer cells go undetected on tests and the cancer begins to grow and spread. Metastatic breast cancer only occurs in some cases of breast cancer and researchers are trying to determine why that is.

Specifically, metastatic breast cancer is caused when the cancer cells invade the lymph nodes and blood vessels. Because the blood vessels and lymph nodes carry fluid throughout the body, it allows the cancer cells to travel to various organs and invade the tissues. The cancer cells may develop small tumors in the new locations.

Risk Factors

Any type of breast cancer has the potential to spread, however, there are some specific risk factors that may increase the likelihood of your cancer metastasizing. These risk factors include:

• Type of breast cancer. There are certain types of aggressive breast cancers (HER2-positive and triple-negative breast cancer), which are difficult to treat, that are more likely to spread.
• Rate at which the cancer grows. Cancer that grows more rapidly has a greater likelihood of spreading to other areas.
• The stage at diagnosis. If the cancer has already spread to the lymph nodes or is very large, it is more likely to spread to other areas of the body.

Diagnosis

If metastatic breast cancer is suspected, your doctor may order further testing. These tests include:

• Blood tests. These tests will get a complete blood count and comprehensive metabolic panel.
• Imaging tests. These tests include an MRI, CT, bone scan, or PET. Imaging tests can detect abnormalities in tissues and detect signs of cancer.
• Biopsy. A biopsy is when a tissue sample is collected and sent to a lab to be analyzed.
• Bronchoscopy. This test is used if a suspicious or abnormal-looking spot is found on your lungs. It uses a scope to look inside your lungs.
• A tap. This procedure removes fluid from an area where there is a tumor or suspected cancer. The fluid will then be sent to a lab for analysis and determine if the cells are cancerous.

Treatment

Treatment for metastatic breast cancer is dependent on several factors. Your care team will create a treatment plan based on what areas of the body cancer has spread to, past breast cancer treatments, symptoms, and how the cancer cells look and behave. Treatment for metastatic breast cancer is systemic, in that it treats the entire body. Typical treatments may include:

• Chemotherapy
• Hormonal therapy
• Immunotherapy
• Targeted therapy
• Surgery
• Radiation
• Clinical trials

Additionally, your provider will test the metastases to determine the biology of the tumor, which helps dictate the treatment plan. Testing the tumor informs treatment by determining the following:

• Hormone receptor (estrogen and progesterone) status. This test determines if the cancer is hormone receptor-positive. If it is, hormonal therapy may be the first treatment approach.
• HER2 status. This is a protein (human epidermal growth factor receptor 2) that is overexpressed on some breast cancer cells, and it may respond best to specific HER2-targeted therapies.
• PIK3CA gene mutation. Your healthcare provider may test for this if the tumor hormone receptor-positive and HER2-negative. There are specific targeted therapies to treat this gene mutation.
• PD-L1 status. Tumors that test hormone receptor-negative and HER2-negative may be tested for PD-L1. If it tests positive, it may be recommended to receive a combination of immunotherapy and chemotherapy.

Treatment for metastatic breast cancer continues for an indefinite amount of time. Some patients may decide to decrease, change, or stop treatments if the side effects become intolerable. The main objectives of treatments are to extend survival rates and enhance the quality of life while living with metastatic breast cancer.

Prevention

There is no known prevention to stop breast cancer from metastasizing. However, you may be able to decrease your risk of developing metastatic breast cancer if the original breast cancer is caught early enough. Staying on top of routine breast exams and mammograms can help healthcare professionals diagnose breast cancer earlier. Additional preventative measures that may decrease the risk of developing breast cancer include:

• Maintaining a healthy weight
• Staying physically active
• Avoiding alcohol or drinking in moderation
• Breastfeeding
• Avoid taking combined hormone replacement therapy

Complications

Complications of metastatic breast cancer depend on where the cancer has spread and what types of treatments are being administered. The main areas metastatic breast cancer spreads to are the bones, lungs, liver, and brain. The most common complications patients face are pain, fatigue, and weight loss.

• Bone metastasis. This may cause fractures to occur more easily and frequently, bone pain, spinal cord compression, and hypercalcemia (too much calcium in the blood).
• Liver metastasis. This may cause jaundice, abdominal pain, shoulder pain, itching, bleeding, or confusion.
• Brain metastasis. This may cause seizures, weakness, balance problems, numbness, vision issues, headaches, personality changes, or loss of consciousness.
• Lung metastasis. This may cause chest pain, shortness of breath, pneumonia, pleural effusion, bleeding in the lungs, or obstruction of airways.