Metastatic breast cancer can cause various complications, either due to the cancer itself or side effects of treatments. Complications can include blood clots, pain, and wasting syndrome.

Metastatic breast cancer is a cancer that has spread to distant areas of the body, most commonly to the lungs, liver, and bones.

This article looks at potential complications of metastatic breast cancer and how they may affect the body.

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General complications that may occur with metastatic breast cancer include:

  • Blood clots: Metastatic cancer can increase the risk of blood clots, as well as some cancer treatments.
  • Pain: The cancer or treatments may cause pain, muscle and joint aches, or painful conditions, such as nerve damage.
  • Cachexia: Cachexia, or wasting syndrome, is severe weight and muscle loss and may affect up to 80% of people with metastatic cancer.

If breast cancer spreads to the bone, complications may include the following:

Bone pain

Bone pain may be one of the first signs of bone metastases.

The pain may be sporadic at first but may become constant over time. A person may experience worse pain at night and find that it improves with movement.

Medications, such as pain relievers and bisphosphonates, and treatments, such as radiation therapy, may help treat bone pain.

Spinal compression

If breast cancer spreads to the bones of the spine, it can put pressure on the spinal cord and cause compression.

Spinal cord compression is a serious complication that, without treatment, may paralyze a person. Experts consider it a medical emergency, and people will need to seek medical help immediately.

Symptoms of spinal cord compression include:

  • back or neck pain
  • numbness in the legs or abdomen
  • leg weakness
  • loss of control of bowel movements or urination

Surgery and radiation therapy can help treat spinal compression.


Hypercalcemia is the term for high calcium levels in the blood. Bone metastases can increase the amount of bone that cells break down, releasing excess calcium into the blood.

If people have hypercalcemia, they may experience:

  • lethargy or sleepiness
  • constipation
  • increased thirst
  • muscle weakness and aches
  • confusion
  • kidney failure
  • coma

Treatment may include intravenous (IV) fluids and bisphosphonates.


Bone metastases can weaken the bone and increase the risk of fractures. People may experience sudden and severe pain if they have a fracture. Fractures most commonly occur in the spine, arms, or legs.

Bisphosphonates may help reduce the risk of fractures. People may have surgery to implant a metal rod to strengthen a weakened bone.

Breast cancer can cause the following lung complications.

Pleural effusion

Lung metastases may cause pleural effusion. Pleural effusion is a buildup of fluid in the lining of the lung, known as the pleural space.

Pleural effusion can compress the lungs and cause chest pressure, shortness of breath, and coughing.

Thoracentesis is a procedure for treating pleural effusion using a needle to drain the excess fluid.

Coughing up blood

The medical term for coughing up blood from the lungs is hemoptysis, which may occur with breast cancer that has spread to the lungs.

People may have systemic treatments to target lung metastases, such as chemotherapy, targeted therapy, hormone therapy, or immunotherapy.

The following are complications from metastases that can affect the liver.


Breast cancer liver metastases may cause jaundice, a yellowing of the skin and whites of the eyes. Other symptoms of liver metastases may include:

  • fatigue
  • weakness
  • abdominal discomfort or pain
  • weight loss
  • a loss of appetite
  • swelling in the legs

Itching is also a common symptom of cancer affecting the liver.

Blocked bile ducts

The bile ducts are small tubes that carry bile from the liver to the small intestine. Breast cancer metastases may cause a bile duct blockage, although this is rare.

Jaundice can be a sign of a blocked bile duct.

The following complications affecting the brain can develop due to advanced breast cancer.


If cancer spreads to the brain, tumors may cause swelling in certain areas of the brain. Headaches are a common symptom of brain metastases.

People may also experience changes in their mental state, confusion, memory problems, or behavioral changes.

Steroids, such as dexamethasone, can help decrease swelling and reduce symptoms. Surgery and radiation therapy can also help manage symptoms.


A seizure is an abnormal burst of electrical activity in the brain and may occur with brain tumors. Seizures may occur in around 10–20% of people with brain metastases.

Anti-seizure medications may help treat seizures with brain metastases and can help prevent them from recurring.

A person may also require:

  • radiation therapy
  • stereotactic brain surgery, which aims to remove the tumor from the brain
  • steroids


If a brain tumor affects the blood supply to the brain, it may cause a stroke. Symptoms of a stroke include:

  • sudden weakness or numbness affecting one side of the body
  • difficulty speaking
  • changes in vision
  • dizziness
  • a headache
  • a loss of balance

If people have symptoms of stroke, they will need immediate medical attention.

Treatment for breast cancer can also lead to complications.


Lymphedema is a buildup of fluid in the tissues due to impaired lymphatic system function.

Breast cancer and treatment may affect how lymph flows through the lymphatic system. Removal of the breast and underarm lymph nodes may lead to lymphedema.

Symptoms of lymphedema include swelling in the arms or legs.

Treatment may include exercise, compression devices, and infection prevention.

Nerve damage

Chemotherapy for metastatic breast cancer may cause damage to the peripheral nerves. People may experience numbness, tingling, or weakness in the hands or feet.

Heart problems

Certain breast cancer treatments, such as some types of chemotherapy, radiation therapy, and targeted therapy, may lead to heart problems, including heart disease and heart failure.

However, the risk of dying from breast cancer is much higher if people do not receive the appropriate treatment. If people are concerned about how their treatment will affect them, they should speak with a doctor.

Breast cancer can cause various complications if it spreads to distant areas of the body. People should let a healthcare professional know as soon as they experience signs of complications.

Medications and treatments can help manage symptoms and may prevent them from progressing.