Complications of Advanced (Metastatic) Breast Cancer

Potential Problems Resulting From Stage 4 Breast Cancer

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Advanced (stage 4) breast cancer involves metastases, or the spread of the cancer to other parts of the body, which can cause several complications. These issues can vary depending on the sites affected and treatment used, but include a range of concerns from blood clots and muscle wasting to shortness of breath and seizures. Fortunately, unlike common side effects, these potential complications are much less common, and you may not experience many or any of these problems.

Many of the possible complications of advanced breast cancer are treatable, and treatments are most effective when they are started sooner rather than later. In some cases, recognizing a complication ahead of time can prevent serious problems, including paralysis or even death.

stage 4 metastatic breast cancer complications

Verywell / Brianna Gilmartin

General Complications

Some general complications associated with metastatic breast cancer are possible no matter where your cancer has spread or the type of treatments you've received or are receiving now.

Blood Clots

Risk factors for blood clots include having metastatic cancer, undergoing some of the treatments for the disease (such as chemotherapy), and bed rest. Blood clots with cancer are extremely common, cause considerable illness, and can be fatal.

These blood clots often begin in the legs or pelvis (deep vein thrombosis) and can break off and travel to the lungs (pulmonary embolism). Symptoms to be aware of include:

  • Redness
  • Swelling
  • Tenderness of your legs
  • Sudden shortness of breath
  • Sudden severe chest pain
  • Lightheadedness
  • Unconsciousness

When caught in time, blood thinners can be used to resolve the clots.


Pain with metastatic cancer can be variable and often depends on the location of metastases. Pain can interfere with your quality of life, and keeping that high is a primary goal in treating stage 4 cancer.

Talk to your doctor about pain control for people with cancer. Many options are available, and most people, even with severe end-stage disease, can be comfortable.


Cancer cachexia is a challenging issue with advanced cancer. It's a syndrome of involuntary weight loss, muscle wasting, and reduced appetite. It reduces quality of life and is felt to be the direct cause of death for 20 percent of people with cancer. If you're struggling with loss of appetite or have lost weight, bring it up with your doctor.

While weight loss is what gets noticed, cachexia appears to begin before weight loss starts. Significant research looking at ways to prevent and treat this problem is ongoing. While it sounds counterintuitive, exercise is helpful.

Complications Related to Bone Metastases

The bones are the most common site to which breast cancer spreads. Progress is being made not only in treating these metastases but looking at ways to prevent them in the first place.

For those who have breast cancer with bone metastases, the newer bone-modifying drugs, such as bisphosphonates and denosumab, may reduce the risk of complications such as fractures. Multiple complications may result from bone metastases.


The pain due to bone metastases can be excruciating, which can vastly decrease quality of life. However, many of the medications for severe pain cause fatigue and drowsiness.

Radiation therapy is very effective at reducing pain due to these metastases. Bone-modifying drugs don't reduce pain to the same degree, but they can be helpful in combination with these other treatments.

Pathological Fractures

A pathological fracture occurs when a bone breaks through a weakened area. Depending on the location, a fracture of this sort can greatly decrease mobility.

Spinal Cord Compression

Spinal cord compression due to cancer is a medical emergency. When bone metastases occur in the lower spine, they can cause the spine to compress and press on nerves that are important in helping you walk, urinate, and have bowel movements.

A very serious form of microfracture in the spine can lead to vertebrae in the back collapsing down on themselves, which is called a compression fracture. When cancer cells in this region result in nerve compression, a medical emergency known as cauda equina syndrome may occur.

Without prompt treatment to stabilize the spinal cord, a person may end up paralyzed in the lower extremities in addition to not being able to control her bladder or bowels.


When tumor breaks down bone, it results in the release of calcium into the bloodstream, a condition called hypercalcemia of malignancy. (There are other mechanisms in cancer that can increase calcium in the blood as well.)

Early on, this may cause:

  • Nausea and vomiting
  • Increased thirst
  • Weakness
  • Muscle aches

It can progress to serious symptoms, including:

  • Confusion
  • Abnormal heart rhythms
  • Coma
  • Death

Complications Related to Lung Metastases

The lungs are the second most common site to which breast cancer spreads, with lung metastases occurring at some point in roughly a third of people with metastatic breast cancer.

The symptoms can vary from none (when lung metastases are found on a scan alone) to significant shortness of breath. In addition to regular treatments for metastatic lung cancer, local treatments are now being used for some people who only have a few lung metastases, and this appears to improve life expectancy.

Lung metastases are related to several possible complications.

Shortness of Breath

Shortness of breath can often be controlled with medications such as morphine. If it's caused by an obstruction, a stent may be placed.

Surprisingly, oxygen doesn't seem to be very helpful in reducing the sensation of shortness of breath.


The presence of metastases in the lungs, especially near the airways, can result in the accumulation of fluid and bacteria deep in the lungs. With the narrowing of the airways, people may develop recurrent pneumonia.

This can be more serious if your white blood cell count is reduced due to chemotherapy, and it often requires hospitalization and intravenous antibiotics.

Coughing Up Blood

Coughing up blood may occur, especially when metastases are near the large airways. Even a small amount—like a teaspoon—is considered a medical emergency. Coughing up a third of a cup of blood has a mortality rate of around 30 percent.

Don't ever ignore it if you cough up blood, even if it doesn't seem like much. When diagnosed promptly, a procedure can often stop the bleeding, whether mild or severe.

Malignant Pleural Effusion

malignant pleural effusion is a condition in which fluid and cancer cells build up between the membranes (the pleura) that line the lung. The severity varies depending on the amount of fluid present, as well as how rapidly it accumulates.

A small pleural effusion may not need any treatment. A large pleural effusion, though, can compress the lungs and lead to severe pain and shortness of breath.

The first step in treatment is usually a thoracentesis, in which a needle is inserted through the chest wall into the pleural space to drain the fluid. Unfortunately, the fluid often recurs.

Options then include:

  • Recurrent draining
  • Inserting a stent so effusions can be drained at home
  • A procedure called pleurodesis, in which a chemical that causes inflammation is inserted into the pleural space, which results in "gluing" of the membranes together so that fluid may not re-accumulate

Pulmonary Hemorrhage

Pulmonary hemorrhage, or bleeding into the lungs, isn't common but may occur. This is a medical emergency and may be fatal without prompt treatment.

Be sure to get immediate medical attention for symptoms that may be related to pulmonary hemorrhage, which include:

  • Difficult or labored breathing
  • Cough
  • Fever
  • Acute respiratory failure

Treatment depends on whether the bleeding is localized (coming from one place) or diffuse (coming from numerous places.)

Obstruction of the Airways

When metastases grow near or into the airways, they may cause an obstruction. This can lead to:

  • Shortness of breath
  • Infections such as pneumonia

If an obstruction is severe, doctors can place a stent in the airway to hold it open.

Complications Related to Liver Metastases

Liver metastases may not cause any symptoms unless the metastases are near the major vessels and ducts of the liver. If you have symptoms, you may notice:

  • Jaundice (yellowing of the skin and whites of the eyes )
  • Abdominal pain
  • Shoulder pain
  • Hiccups

Often, a large part of the liver needs to be replaced by the tumor to cause significant symptoms. When this happens, several complications may arise.


With liver dysfunction, fluid can build up in the peritoneal cavity, causing ascites. If your abdomen becomes very distended, it can be painful and cause shortness of breath (especially if you also have lung metastases).

Doctors may do a procedure called a paracentesis in which a needle is inserted through the skin and into the abdominal cavity to drain off the fluid.


With extensive metastases, confusion and lethargy may result due to the build-up of toxins in the body. Get medical attention if this happens.


The liver is responsible for making clotting factors for the blood. If this organ is largely non-functioning, the result can be an insufficient amount of clotting factors, which can lead to bleeding and anemia.

In case of an injury that won't stop bleeding, get medical attention right away.


You may not think of itching as a serious complication, but the itching that can accompany liver metastases can be severe.

It occurs due to the build-up of bile acids in the blood and skin. Ask your doctor about medications to reduce this symptom.

Complications Related to Brain Metastases

Brain metastases are also common in breast cancer and may result in any number of symptoms, some which can be life-threatening.

You may experience a complication of brain metastases before knowing that cancer has spread to your brain.


You may be familiar with generalized tonic-clonic (formerly called) grand mal seizures, or tonic-clonic, in which a person becomes unconscious and shakes violently. These are possible with brain metastases.

Seizures can cause a variety of symptoms based on the type, ranging from muscle stiffness to the appearance of not being aware of surroundings and more.


Brain metastases can lead to:

  • Weakness
  • Numbness
  • Loss of balance

Any of those symptoms can contribute to the risk of falls, which can result in serious injury and disability. If brain metastases are present, it's important to be extra careful about fall prevention.

Other complications of brain metastases may include:

  • Visual problems, such as double vision or loss of vision
  • Sudden changes in mental status or personality
  • Loss of consciousness

The treatment for complications of brain metastases is often radiation. If only one or a few metastases are present, a specialized form of radiation therapy called stereotactic body radiotherapy (SBRT) may be used in an attempt to eradicate the metastasis.

Complications Due to Other Metastases

Breast cancer can spread to nearly any region of the body. If you have symptoms, even if they're seemingly unrelated to your cancer, make sure to talk to your oncologist.

Other common metastases complications include kidney failure, pericardial effusion, and brachial plexus injury.

Kidney Failure

Kidney failure may occur not only due to metastases to the kidneys (not an uncommon site) but due to medications you are taking, dehydration, and more.

Symptoms of kidney failure include:

  • Decreased urine output
  • Fluid retention/puffiness of the legs, ankles, or feet
  • Shortness of breath
  • Fatigue
  • Confusion
  • Nausea
  • Weakness
  • Irregular heartbeat
  • Chest pain or pressure

And in severe cases:

  • Seizures
  • Coma

Get immediate medical care for symptoms of kidney failure.

Pericardial Effusion

Just as breast cancer can spread to the lining of the lungs, it can spread to the lining of the heart and cause pericardial effusion.

When fluid builds up between the membranes lining the heart, your heart has to work harder. The heart rate usually speeds up to make up for the smaller volume it's pumping out.

If the fluid builds up fast or is extensive, it can lead to a condition known as pericardial tamponade, basically restricting the heart so much that it is unable to beat. When this condition occurs due to cancer metastases, a third of people die before it can be diagnosed and treated. Fortunately, this complication isn't common.

Be certain you talk to your doctor if you note any increased shortness of breath or a rapid heart rate.

Brachial Plexus Injury

When cancer spreads into the tissues under the arm, it may damage a group of nerve fibers known as the brachial plexus. This can cause weakness or paralysis in the arm on that side.

Brachial plexopathy due to breast cancer affects only 1 in 200 women, but is often a very frustrating complication when it occurs.

Complications Due to Treatment

Other serious complications that may occur are similar to those that can happen to people with early-stage breast cancer. These can happen during and after treatment.

Heart Disease

Both chemotherapy and radiation therapy can damage the heart. Heart disease may appear many years after the initial treatment and can range from coronary artery disease to heart failure to valve problems.

Most common is heart failure, which often declares itself with symptoms of shortness of breath, swelling of the extremities, and coughing up pink, frothy sputum.

Always get medical help if you have symptoms of heart disease.


If you are on chemotherapy, your doctor has likely warned you about developing a fever (fever of neutropenia). A fever that wouldn't be alarming in someone else could be life-threatening in you.

When your immune system is suppressed, you are not only more susceptible to infections, but your ability to fight off an infection is compromised. Even mild infections may require hospitalization and intravenous antibiotics.

If you believe you may have an infection, don't wait. Call your oncologist.

Allergic Reactions

When you're living with stage 4 breast cancer, you may be using several medications, including cancer treatments and medications to manage your symptoms. Even if you've taken a medication 100 times, the next dose could result in a severe allergic reaction.

Ideally, everyone should be aware of the symptoms of anaphylaxis, a severe allergic reaction, as this can be life-threatening. If you notice any swelling of your neck, tongue, or face, the development of hives, or lightheadedness, seek medical attention.

Psychological Complications

As with some of the "milder" symptoms above, you may not think of depression as a complication of metastatic cancer, but it is a very important. This battle is a tough one that can affect the mental health of any person, whether they come across as a "fighter" or not. While the risk of suicide is lower in breast cancer than with some other cancers, it is something that, unfortunately, still occurs.

The goal of treatment is to extend your years while giving you the best quality of life possible. If anything is interfering with your ability to enjoy your family and friends, it should be addressed, either by your oncologist, a palliative care specialist, or a cancer therapist.

A Word From Verywell

These are some of the potential complications that may accompany a diagnosis of metastatic breast cancer, but you may face other, less common issues as well. But also know that many people do not experience complications at all. The important thing is to be aware of your body and talk to your oncologist about any concerns. Frequently, serious complications can be treated if they're found in a timely manner.

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