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Metastatic breast cancer to the bones

Metastatic breast cancer can sometimes travel beyond the breast to the bones, one of the most common locations of spread.


When breast cancer travels to other organs in the body, it’s called metastatic breast cancer. This includes stage IV breast cancer. Metastatic breast cancer can sometimes travel beyond the breast to the bones, one of the most common locations of spread. In the bones, metastatic breast cancer is called bone metastasis, or bone mets.

It’s possible for breast cancer to travel to any bone in the body, but the spine, hips, shoulders, skull, and upper parts of the leg bones near the hips are where it’s most often found. Bone metastasis can lead to weak bones, pain, and a higher risk of fractures. We know the idea of weak, easily broken bones can sound scary. But there are ways to manage bone issues and to protect the bones from some damage.

It’s also important to know that if you’re diagnosed with metastasis to the bone, you can still have an active life that includes exercise. Whether you’re an athlete or you’re new to exercise, you can work with your care team and a physical therapist to create fitness routines that meet your needs and remains safe for your bones.

It’s possible to have bone metastases and metastases in one or more other organs at the same time. Doctors refer to this as “multiple metastasis.” If you have metastases in more than one part of the body, your healthcare team will work to treat the cancer in all sites.

photo depicting knee pain

About bones

Adults have 206 bones in their bodies. These bones may seem solid and unchanging, but in reality, the cells that make up healthy bones are breaking down and building back up constantly. Bones are made up of three types of cells:

  • Osteoclasts, which break down old bone
  • Osteoblasts, which form new bone
  • Osteocytes, which are mature bone cells

When breast cancer spreads to your bones, the cancer interrupts the natural process of bone cells. This can lead to weak bones, pain, and a higher risk of fractures.


What are bone metastases?

Bone metastases are areas of cancer that develop when breast cancer cells travel to the bones. The tumors that develop, sometimes called lesions, can:

  • Make the bones weaker and less dense. These types of tumors are called osteolytic, or simply lytic. Lytic lesions are caused by cancer cells causing old bone to break down without new bone being made, leaving weak spots or holes.
  • Make the bones more dense, but not necessarily stronger. These types of tumors are called osteoblastic, or simply blastic. Blastic lesions are caused by new bone being made without old bone breaking down. This makes the bone harder, but this harder bone can still break more easily than normal bone.

It’s common for people to have lytic and blastic lesions at the same time. Doctors use imaging tests, such as x-rays, to figure out the types of bone lesions a person might have. For lytic lesions, treatment may include bone-strengthening medicines called bisphosphonates. Blastic lesions can be treated with radioactive material injected into a vein, called radiopharmaceuticals. Radiopharmaceuticals can travel to bone metastases and destroy cancer cells.


Who gets bone metastases?

Anyone diagnosed with breast cancer can develop bone metastases. For many people with metastatic breast cancer, the bones are the first location of cancer spread. In fact, almost 70 percent of people with metastatic breast cancer develop bone metastases at some point.

People diagnosed with estrogen receptor-positive metastatic breast cancer are more likely to have bone metastases than people with other subtypes of metastatic breast cancer. But so far, there is no evidence that people of certain ages or ethnicities are more likely to have cancer spread to the bone than others.


What are the symptoms of bone metastases?

Often, first signs of bone metastases are aches and pains that are strong and unexplained. These pains can be caused by the metastases themselves, or by a bone break or fracture. For many people, any unexpected symptom after a cancer diagnosis can trigger fear and anxiety. This is completely understandable, and if this is you, you’re not alone. Knowing that aches and pains are a major symptom of bone metastases may add to this stress, because everyone — cancer or not — has aches and pains from time to time.

It can be hard to know when a new ache is cancer-related. These symptoms may not immediately seem like cancer because there are many health issues that cause aches and pains, including menopause, breast cancer treatments such as aromatase inhibitors, or diseases like arthritis. And there are many ways to break or fracture even the strongest bones. The most important thing for you to do is to let your doctors know if you’re feeling something out of the ordinary so that they can reassure you, or order tests to look into symptoms you experience.

A serious, though rare, complication of bone metastasis is spinal cord compression. In spinal cord compression, a dangerous amount of pressure is put on the spinal cord, a column of nerve tissue that sends signals from the brain to the muscles. Symptoms can include:

  • Lower back pain
  • Burning pain that runs down the arms or back of the legs
  • Numbness in the arms, legs, hands, or feet
  • Trouble urinating
  • Feeling constipated

Spinal cord compression can be very painful, affect your height and posture, and if not treated can sometimes lead to paralysis. Although spinal cord compression is not common, it is a medical emergency typically treated with radiation therapy, and sometimes also surgery. It’s important to call your doctor right away if you experience these symptoms.

If you have a history of breast cancer, even if it was years ago, report any bone pain that lasts 2 weeks or more to your healthcare team. This includes pain that makes you feel the need to see a chiropractor. Your care team can help determine whether you’re experiencing metastatic breast cancer symptoms, side effects related to breast cancer treatment, or something else.


How are bone metastases diagnosed?

Most cases of metastatic breast cancer to the bones are diagnosed after a person tells their doctor about bone-related symptoms. Others are diagnosed when a routine follow-up test shows abnormal results. If a doctor thinks you may have bone metastases, they will order one or more tests to confirm the diagnosis.
Doctors use imaging tests to create pictures of the bones and learn whether cancer has spread to them. These tests include:

  • Bone scans
  • Bone x-rays
  • CT scans
  • MRIs
  • PET scans

Your doctor may also order a blood chemistry test to check for changes in your blood. These tests look for high levels of the mineral calcium and high levels of the enzyme alkaline phosphatase. We all need calcium and alkaline phosphatase, but too much of either in the blood could mean tumors in the bones are causing these substances to break down and get into the bloodstream.

It is important to know that bone density tests (sometimes called DEXA scans), which are frequently ordered in patients with early breast cancer to monitor the effects of hormonal medications on bone strength, do not detect bone metastases.

Sometimes, doctors diagnose bone mets by performing a bone biopsy, performed using a needle to remove a tiny piece of bone and test it for cancer cells. If you have just one suspicious area in the bones, or if it’s been many years since you were diagnosed with early-stage breast cancer, your doctor is more likely to recommend a bone biopsy.


How are bone metastases treated?

Bone metastases and their symptoms are typically treated with systemic treatments that treat cancer cells no matter where they are in the body. These include:

In addition to these standard treatments, doctors may recommend these systemic bone-modifying medicines:

  • Bisphosphonates can make bones stronger and reduce bone pain, and in some cases, stop new bone metastases from forming. The bisphosphonate used most often for metastatic breast cancer in the bones is called zoledronic acid (Zometa).
  • RANK ligand inhibitors, like bisphosphonates, work to strengthen bones and ease bone pain. The most common RANK ligand inhibitor used for breast cancer in the bones is denosumab (Xgeva).

It’s also possible to treat bone metastases locally, in the specific places where cancer cells are found. Local therapies target cancer cells at the site of the metastasis, rather than treating cancer cells all over the body. For metastatic breast cancer in the bones, these are:

  • Surgery to stop bones from breaking and to ease pain. This can include:
    • Surgery to insert metal rods within bone and provide stability
    • Kyphoplasty, in which cement is inserted into certain bones to ease pain
  • Radiation therapy to ease pain

Treatment effectiveness

A diagnosis of breast cancer metastasis can trigger many different, and intense, feelings of uncertainty. It’s absolutely normal to wonder how long treatments may work, and you are not alone if you find yourself in this space. Many people living with a cancer diagnosis look for information about prognosis, the likely outcome or course of disease.

Right now, it’s not possible to predict how long one person with bone metastases might live compared to another. The most recent survival statistics available are not an accurate reflection of how long people are living today. Tracking and compiling survival data takes time, and during that time, new and more effective treatments become available.

Figuring out life expectancy also means looking at breast cancer subtype, how responsive the cancer is to treatment, your health before cancer, and current lifestyle choices, such as smoking and nutritional habits. What we do know is that people living with metastatic breast cancer are living longer.

If you’re curious about your own situation and believe knowing more will help you, talk with your care team. You can also learn more about life expectancy on our MBC prognosis page.

The first step to living well with metastatic breast cancer is to get standard-of-care systemic treatments, such as hormonal therapy, chemotherapy, and targeted therapy. These treatments work to keep the cancer from growing more or traveling further in the body. Treatments specific to bone metastases, such as surgery, radiation, and bone-modifying medicines, are the best next step, because they can help reduce side effects and maintain your quality of life.

Monitoring bone metastases

Once there is a clear diagnosis of bone metastases, you and your doctors will decide on a treatment plan. Part of that plan will involve tests that show how well treatment is working and how strong your bones are. These tests can show whether the bone metastases are growing, spreading, or staying the same, so you and your doctor can continue making treatment decisions and manage side effects.

Tests to monitor bone metastases

We know that it can feel frightening to think about the possibility of weaker bones or bone pain. It can mean changing your routine or avoiding activities you’re used to. But there are always adjustments that can be made to allow you to live a life that is active and fulfilling in many different ways.

Your care team will monitor the bone metastases regularly to control the cancer and to help you figure out what your body can handle as you have treatment. Your doctors may use some of the same tests to monitor bone metastases that were used to diagnose them. This will likely include imaging tests that create pictures of your bones, such as x-rays, CT scans, MRIs, PET scans, and bone scans.

By comparing the pictures over time, your doctors can see if tumors in the bones are growing, shrinking, or changing in other ways in response to treatment. The images will also show doctors how strong your bones are, and whether a bone is at risk of breaking. If a fracture risk is found, they can recommend treatments that reduce the risk.

Your doctors may also order blood tests to monitor bone metastases:

  • Tumor marker tests look for certain proteins or cells that break away from tumors and get into the bloodstream. Cancer cells that enter the blood can travel through the bloodstream and form tumors in other parts of the body. If a tumor marker test shows cancer cells in your blood, your oncologist can work to prevent the cells from forming tumors elsewhere by changing your treatment to better control the cancer.
  • Blood chemistry tests can be used to look for high levels of calcium in your blood. High levels of calcium suggest the bones aren’t building up and breaking down the way they should be, which can be a sign that treatment isn’t working well enough and tumors in the bones are growing or spreading. If a blood chemistry test suggests the tumors might be growing, your doctors will recommend a new treatment.

How often do you need testing?

How often you get which tests depends on your diagnosis and your doctor’s preferences. But it’s common for doctors to recommend imaging tests in patients with metastatic breast cancer every 2-6 months to assess for bone metastases. If they recommend blood tests, a common schedule for tumor marker tests is every 1-3 months. Blood chemistry tests are commonly done every 1-3 months.

Your doctor may also recommend additional tests if you experience bone-related symptoms or side effects. You can always ask your doctor about why different tests are recommended at certain times.


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Reviewed and updated: January 7, 2022

Reviewed by: Nancy U. Lin, MD


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