Bone Metastasis

What Is Bone Metastasis?

Cancer cells that break off from the first tumor (called the primary site) and enter either the bloodstream or the lymph system can reach nearly all tissues of the body. Often these cells will settle in the bones and start growing. These bone metastases (often referred to as "bone mets") can happen anywhere in the body, but they are mostly found in bones near the center of the body such as the spine, ribs, pelvis, and bones near the hips and shoulders.

Bone metastases are not the same as cancer that begins in the bones (primary bone cancer). Bone metastases and primary bone cancer are very different. Primary bone cancer is much less common than bone metastases.

When cancer comes back in a person who appeared to be free of cancer after treatment, it is called a recurrence. Cancer might come back in these places:

• in or near the same place it first started (local recurrence)
• in nearby lymph nodes or in the area where lymph nodes used to be (regional recurrence)
• another part of the body farther away (distant recurrence)

Sometimes the cancer has spread widely when it is first found and doctors cannot find where it first began. This is called cancer of unknown primary. This kind of cancer is covered in another American Cancer Society essay.

Bone metastasis is one of the most frequent causes of pain in people with cancer. It can also cause other problems such as broken bones and high blood calcium levels.

What Causes Bone Metastasis?

A risk factor is anything that increases a person's chance of getting a disease such as cancer. Different cancers have different risk factors. Some risk factors, such as smoking, can be controlled. Others, like a person's age or family history, can't be changed. The risk factors for metastatic cancer are the same as those for cancer in general. Risk factors that can be controlled (for cancer as a whole) are as follows:

• tobacco use
• an unhealthy diet
• not getting enough exercise
• being overweight
• alcohol abuse

How Cancer Cells Spread

Metastasis is the end result of a process that has several steps. Understanding all the steps is a major focus of cancer research. Such knowledge could lead to better ways to prevent metastasis from taking place.

Normal cells are held in place by a substance called extracellular matrix or ECM. ECM is something like the mortar that holds bricks together to form the walls of a building. Most normal cells in our body (except for blood cells) tend to remain in place. But cancer cells are able to detach from the ECM and travel around. However, just breaking loose is not enough. The cancer cells must be able to break through the walls of blood vessels or lymph vessels to travel around the body. Then they must be able to grow in a place that is different from the organ where they started. They must also be able to cause the body to grow new blood vessels so they can receive food and oxygen.

Some cancer cells carry substances that cause them to stick better to the surfaces of cells in different organs. Cancers that tend to spread to bone may attach better to bone cells. In other cases, bone cells release something that causes cancer cells to grow faster. As we learn more about these steps, we hope to find new ways to treat or even prevent bone metastasis.

What Happens When Cancer Grows in Bones?

Often, the cancer cells make substances that damage the bones. Usually these substances can cause the bones to dissolve and weaken. This can lead to broken bones and large amounts of calcium being released into the blood. Sometimes, the cancer causes the bones to become harder. This is called sclerosis. Both types of bone metastases can cause pain. When the cancer dissolves the bone, the bone can break (fracture). Fractures occur much less often with cancers that cause sclerosis

How Is Bone Metastasis Found?

The first symptom of bone metastasis is almost always pain. If you have cancer and begin to have pain in a bone, you should tell your doctor right away. Sometimes, if the cancer isn't treated promptly, the bone may break. Of course, the source of the bone pain could be something other than cancer, such as an infection or arthritis.

Symptoms of Bone Metastasis

Bone pain: The pain often comes and goes at first. It tends to be worse at night, and it may be relieved by movement. Later on, it becomes constant and may be worse during activity.

Broken bones (fractures): Bones can break, causing severe pain and limiting movement. The bones most likely to break are the long bones of the arms and legs and the bones of the spine. Sudden pain in the middle of the back is sometimes a sign of a bone breaking.

Pressure on the spinal cord: Cancer in the backbone can press on the spinal cord. This is a serious problem. Not only does it cause pain, but the pressure can damage the spinal cord so that the legs become numb or even paralyzed. Sometimes the first symptom of this problem is trouble urinating because nerves from the spinal cord control the bladder.

High blood calcium: High levels of calcium (hypercalcemia) are caused by release of calcium from bones. This can cause loss of appetite, nausea, thirst, and tiredness. It can even lead to a coma if not treated.

It is important to report any new bone symptoms or changes in old symptoms to the doctor or nurse right away. Finding and treating these symptoms early can help reduce the chances of further problems later on.

Sometimes, bone metastases are found before they have a chance to cause any symptoms. In these cases, lab tests, x-rays, or bone scans point to possible bone metastasis.

Tests to Find Bone Metastasis

X-rays: X-rays will only show bone metastasis if the cancer has destroyed about half of the bone. But x-rays can also find breaks in bones that have been weakened by metastasis.

Bone scan: This test helps show if a cancer has spread to the bones. A radioactive substance is injected into a vein and collects in diseased bone cells anywhere in the body. These areas are called "hot spots." But arthritis, infection, or other bone diseases can also cause hot spots. Bone scans can find metastases much sooner than normal x-rays.

CT scans: The CT scan (computed tomography) uses an x-ray beam to take a series of pictures of the body from many angles. A computer combines the pictures to form a detailed image. This test can help show if the cancer has spread to the bones. CT scans can also be used to guide a needle into an area that might be metastasis. The needle takes out a sample of tissue that can be looked at under a microscope to see if cancer cells are present.

CT scans take longer than x-rays and you need to lie still on a table for 15 to 30 minutes while they are being done. But they are getting faster all the time. Often after the first set of pictures is taken you will receive an injection of a "dye" that helps better outline structures in your body. A second set of pictures is then taken. You might feel a bit confined by the ring-like machine that rotates around you while the pictures are being taken.

MRI scans: Like a CT scan, the MRIs display a cross-sectional picture of the body. But the MRI uses radio waves and strong magnets instead of x-rays. MRI scans are especially useful for looking at the spine and spinal cord. MRI scans take longer than CT scans, often up to an hour. For this test you have to be placed inside a tube-like machine, which can upset people with fear of enclosed spaces.. The machine makes a thumping noise that you might

PET scans: PET (positron emission tomography) uses a form of sugar that contains a radioactive atom. The sugar is injected into a vein and cancer cells in the body quickly absorb it. A special camera is used to spot areas where the sugar collects. PET scans are useful in finding cancer that has spread to the lymph nodes. They are also helpful when the doctor thinks the cancer has spread but doesn�t know where.

Blood and urine tests: Some types of cancer release certain substances (tumor markers) into the bloodstream or urine. The cancer can also cause organs to produce high levels of certain chemicals. Blood and urine tests can help point to these problems.

Biopsy: For a biopsy a small sample of cells or tissue is removed and sent to the lab to be looked at under a microscope. If you have had cancer in the past, your doctor can usually tell if you have metastasis based on the bone scan or x-rays. You would not need a biopsy. But if the results were not clear, the doctor will do a biopsy. Since there is more than one type of biopsy, be sure to ask your doctor to explain the test you are having so you will know what to expect.

How Is Bone Metastasis Treated?

This information represents the views of the doctors and nurses serving on the American Cancer Society's Cancer Information Database Editorial Board. These views are based on their interpretation of studies published in medical journals, as well as their own professional experience.

The treatment information in this document is not official policy of the Society and is not intended as medical advice to replace the expertise and judgment of your cancer care team. It is intended to help you and your family make informed decisions, together with your doctor.

Your doctor may have reasons for suggesting a treatment plan different from these general treatment options. Don't hesitate to ask him or her questions about your treatment options.

Treatment for bone metastasis depends on where the cancer started, which bones it has spread to, and whether any bones are weak or broken. Other factors include certain features of the cancer cells, your general state of health, and which treatments you have already received.

Most doctors will treat bone metastasis by treating the cancer that caused it. This is usually done with chemotherapy ("chemo") or with hormonal therapy. These are called systemic treatments because the drugs or hormones enter the bloodstream and reach cancer cells throughout the body. Also, drugs called bisphosphonates can help to make bones stronger and prevent breaks. They can be used along with chemo or hormone therapy. If these treatments work, then the symptoms of bone metastasis will go away and new symptoms are not likely to happen soon.

The doctor may also need to treat the bone problems to relieve pain or to keep the bones from breaking. Radiation might be used to relieve pain by killing the cancer cells. Surgery is sometimes needed to strengthen a bone and keep it from breaking. It can be much easier to prevent a bone from breaking than to repair it once it has broken.

This section begins with a listing of the types of treatments used for people with metastatic cancer, followed by information about treating bone metastases.

For more details about treatments for cancer that has spread from a specific type of primary cancer (for example, prostate cancer), please refer to each cancer type. You�ll find this information in the sections on treatment of advanced cancer, stage IV cancer, or recurrent cancer in those documents.

Chemotherapy: Chemotherapy ("chemo") refers to the use of drugs to kill cancer cells. Usually the drugs are given into a vein or by mouth. Once the drugs enter the bloodstream, they reach throughout the body. Chemo is used as the main treatment to cure some metastatic cancers. In many cases, chemo can shrink tumors. This can help people feel better and reduce pain.

Chemo drugs kill cancer cells but also damage some normal cells. So it can cause some side effects. These side effects will depend on the type of drugs given, the amount taken, and how long the treatment lasts. Side effects could include the following:

• hair loss (hair grows back after treatment)
• mouth sores
• increased chance of infection (from a shortage of white blood cells)
• bruising or bleeding easily (from a shortage of platelets)
• tiredness (from a shortage of red blood cells)
• loss of appetite
• nausea and vomiting
• diarrhea or constipation

If you have side effects, your doctor or nurse can suggest steps to ease them. For example, there are drugs to help control and prevent nausea and vomiting. The good news is that most side effects will go away when your treatment ends. To learn more about chemo, please see Understanding Chemotherapy: A Guide for Patients and Families.

Hormone therapy: Some hormones promote the growth of certain cancers. For example, estrogen, a hormone made in a woman�s ovaries, sometimes promotes the growth of breast cancer. Likewise, testosterone (made by a man's testicles) promotes the growth of most prostate cancers.

There are several ways to stop these hormones. One way is to remove the organs that make them: the ovaries in women or the testicles in men. More often, drugs can be used to stop the organs from making the hormones or to prevent the hormones from affecting the cancer cells. Side effects of these drugs can include hot flashes, blood clots, loss of interest in sex, and a higher risk of other cancers.

Immunotherapy: These methods help a patient's own immune system fight the cancer. Most of these approaches are still experimental.

Radiopharmaceuticals: These are a group of drugs that have radioactive elements. They are injected into a vein and settle in areas of bone that contain cancer. The radiation they give off kills the cancer cells and relieves some of the pain caused by bone metastases. They are only used for cancer that has spread from another place to the bone.

The major side effect of this treatment is a lowering of blood cell counts (white cells and platelets), which could place you at a higher risk for infections or bleeding, especially if your counts are already low. Another possible side effect is a so-called "flare reaction," where the pain gets worse for a brief time before it gets better.

Radiation treatment: This type of treatment uses high-energy x-rays to destroy cancer cells or to slow their rate of growth. Radiation treatment can be used to cure cancers that have not spread too far from the place where they started. When a cancer has spread to bones, radiation is used to relieve (palliate) symptoms. Radiation may help prevent breaks once the bone has healed or been stabilized with surgery. Radiation will not prevent weakened bones from breaking, though.

The most common way to give this type of treatment is to carefully focus a beam of radiation from a machine outside the body. This is known as external beam radiation. To reduce the risk of side effects, doctors figure out the exact dose and aim the beam as accurately as they can to hit the target.

Radiation treatment for bone metastasis can be given as a large dose at one time, or in smaller amounts over 5 to 10 treatments. Each treatment lasts only a few minutes. This method is a good choice if there are only 1 or 2 metastases that are causing symptoms. If there are many, though, the treatment is more complex.

For more information on radiation treatment, please see the American Cancer Society document, Understanding Radiation Therapy: A Guide for Patients and Families.

Radiofrequency ablation: This technique uses a needle attached to electric current. The needle is placed into a painful tumor that hasn�t improved with radiation treatment. An electric current, given through the needle, destroys the tumor and relieves pain. This is usually done while the patient is in a deep sleep (under anesthesia).

Surgery: When surgery is used to treat bone metastasis (as opposed to primary bone cancer) it is for relief of symptoms rather than cure. Bones can become weak, leading to breaks that don�t heal very well. A metal rod might be used to strengthen the bone and prevent it from breaking. Or, if the bone is already broken, surgery can stabilize the bone and relieve pain.

Surgery for metastases near the spinal cord or large nerves can prevent or relieve symptoms such as not being able to move (paralysis) and severe pain. If surgery is not an option because of poor health or for other reasons, a cast might help to reduce pain and avoid the need to stay in bed.

Pain medicines: There are good ways to treat bone pain. These methods are also safe. In some cases, treatment for pain may also kill the cancer cells, slow their growth, or reduce bone damage. If the treatment you are having does not relieve your pain, you should not be afraid to ask for pain medicines.

Sometimes patients don�t want to take pain medicine because they think they will become addicted or that it will make them too sleepy. In fact, when taken to relieve pain, these medicines rarely cause addiction. And drowsiness can be controlled. Being free of pain can help patients focus on the things that are important to them.

If you are in pain, take your medicines on a regular schedule. It is better to prevent pain rather than to treat it once it starts. For more information about treating pain, please see, Pain Control: A Guide for People with Cancer and their Families.

Bisphosphonates: These are drugs used to treat weak bones (osteoporosis). They are also used to treat patients whose cancer has spread to their bones. These drugs help reduce bone pain, slow down bone damage, lower blood calcium levels, and lower the risk of bones breaking.

These drugs may be taken by mouth or given through a vein. Because they often cause irritation in the digestive tract, they are usually given into a vein every 3 to 4 weeks. The most common side effects are tiredness, fever, nausea, vomiting, low red blood cell count and bone or joint pain. But these problems might also be caused by the cancer itself or other drugs the patient is taking. Joint and muscle pain can often be relieved with a mild pain reliever.

Lately, doctors have noticed a very distressing side effect among some patients getting bisphosphonates. These patients have damage to the jawbone. Part of the upper or lower jaw has died. This can lead to loss of teeth in that area or infections. Doctors don�t know why this happens or how to prevent it other than stopping treatment with the drugs.

Some doctors suggest that patients have a dental checkup and have any tooth or jaw problems treated before they start taking bisphosphonates.