Metastatic, or stage 4, breast cancer is a type of breast cancer that has spread to another part of the body.

Breast cancer metastases may spread anywhere in the body, but they most commonly affect the bones, brain, liver, or lungs. Treating metastatic cancer typically involves managing the symptoms and preventing the cancer from progressing.

This article covers everything from how it happens and common symptoms to testing, diagnosis, and treatment.

Metastatic breast cancer occurs when the cancer has spread to other parts of the body. The National Breast Cancer Foundation note that the most common areas affected by breast cancer metastases include the:

  • bones
  • brain
  • liver
  • lungs

Metastatic breast cancer most often affects the bones first.

The National Cancer Institute (NCI) state that the cancer cells typically spread by following a series of steps. The cells:

  1. grow into or invade nearby healthy tissue
  2. penetrate the walls of nearby lymph nodes or blood vessels
  3. travel through the lymphatic system and bloodstream to other areas in the body, such as the bones, brain, lungs, or liver
  4. invade blood vessel walls and move into surrounding healthy tissue at the new location
  5. grow in the new tissue until a small tumor forms
  6. develop new blood vessels to establish a blood supply for the tumor so that it continues to grow

Approximately 30% of people with early stage breast cancer will eventually receive a diagnosis of metastatic breast cancer. This diagnosis can occur months or even years after the initial breast cancer diagnosis.

When breast cancer spreads to other areas of the body, the cancer cells are still breast cancer cells. In other words, even if the cancer metastasizes in the bones, the tumor will consist of breast cancer cells, not bone cancer cells.

Some people may have metastatic breast cancer and not experience symptoms. If symptoms do occur, they may vary based on the size of the tumors and where in the body they have spread.

Here are some common signs and symptoms of metastatic cancer that has spread to certain areas of the body:

  • Bones: Symptoms may include bone pain and fractures, commonly in the spine, pelvis, ribs, or the long bones in the arms or legs.
  • Brain: Symptoms may include dizziness, headaches, or seizures, as well as slurred speech, vision issues, and problems with memory.
  • Liver: Symptoms may include abdominal swelling or jaundice, and this may sometimes lead to poor appetite, fatigue, weight loss, or fever.
  • Lungs: Symptoms may include shortness of breath, a persistent cough, and general chest discomfort or pain.

There are a variety of tests that a doctor may use to diagnose metastatic breast cancer. A person may undergo one or more of the following diagnostic tests to look for cancer spread throughout the body:

  • bone scans
  • chest X-rays
  • CT or CAT scans
  • MRI scans
  • PET or PET CT scans
  • blood tests

According to one article, a doctor should take the time to explain what each recommended test is for. They should discuss the following:

  • why the test is necessary
  • how it is conducted
  • what the results can mean
  • any side effects or risks of the test
  • any other exams that may be necessary
  • whether or not there are any alternative options
  • what may happen if a person decides not to have the exam
  • when to expect to receive and discuss the results with a doctor

A person does have the right to refuse any test their doctor recommends.

There is currently no cure for metastatic breast cancer. According to the NCI, treatment can help:

  • slow or stop the spread of the cancer
  • relieve the symptoms to improve quality of life
  • prolong life

With treatment, a person can live for several months or years with metastatic breast cancer.

A person with metastatic breast cancer should work with a doctor to understand their options. Although early treatment may help improve the outlook, a person should take some time to better understand the diagnosis and the various treatment options available to them.

Some common treatment options a doctor may recommend for metastatic breast cancer include:

  • chemotherapy, to damage or destroy cancer cells throughout the body
  • radiation therapy, to control cancer growth in specific areas and ease symptoms such as pain
  • targeted therapy, which targets specific receptors and abnormal growth pathways to help prevent growth
  • hormone therapy, to help to shrink or slow the growth of hormone receptor-positive metastatic breast cancer
  • clinical trials, which test new medications or therapies aiming to improve cancer care
  • complementary and holistic medicine — such as hypnosis, acupuncture, massage, meditation, and yoga — to help ease the symptoms, reduce treatment side effects, and improve quality of life
  • palliative care, which can help relieve symptoms from the cancer and its treatments

Because there is currently no cure for metastatic breast cancer, treatment will continue until a person is no longer benefiting from it. The natural history of metastatic breast cancer is that a person’s cancer becomes resistant to a given therapy over time. At that point, a doctor should discuss other options and next steps with the person.

If treatments are no longer effective at slowing cancer spread or alleviating the symptoms, a doctor may recommend stopping treatment. A person may also decide at any time to no longer pursue treatment.

The NCI indicate that this may be a time for the person and their family to discuss and plan for end-of-life care. At this time, the person can still receive palliative care to help keep them as comfortable as possible.

Metastatic, or stage 4, breast cancer occurs when the cancer cells have spread to other areas in the body. It often affects the bones, brain, liver, and lungs.

There is currently no cure for metastatic breast cancer. Treatment focuses on slowing the growth and spread of the cancer as well as reducing the symptoms and improving quality of life.