How are bone metastases diagnosed?

If you are diagnosed with cancer, bone metastases may sometimes be found before they have a chance to cause any symptoms. Your doctor may order lab tests and imaging tests (such as x-rays or bone scans) to see how far the cancer has spread. This may be done before, during, and after treatment. These tests may show bone metastases.

In other cases, a symptom such as bone pain may be the first sign of bone metastases. Imaging tests or other tests may then be done to confirm this is what is causing the pain.

Signs and symptoms of bone metastases

Bone pain

Bone pain is often the first symptom of cancer that has spread to the bone. The pain often comes and goes at first. It tends to be worse at night and may be relieved by movement. Later on, it can become constant and may be worse during activity.

It is important to tell your doctor right away about any new pain that might be coming from a bone. The bone might be so weakened that it will break. This can often be prevented if the bone metastasis is found early. Your doctor will want to x-ray the painful area and may use other imaging tests. Other diseases, such as bone infections, arthritis, or just being very active can also make bones hurt.

Fractures

Bones weakened from metastatic cancer may break (fracture). The fracture can happen with a fall or injury, but a weak bone can also break during everyday activities. These fractures often cause sudden, severe pain. The pain may keep you from moving much at all. In some cases, a fracture is the first sign of bone metastasis.

The most common sites of fractures are the long bones of the arms and legs and the bones of the spine. Sudden pain in the middle of the back, for example, is a common sign of a cancerous bone in the spine breaking and collapsing. This is an emergency that requires treatment right away to prevent further damage.

Symptoms of spinal cord compression

Cancer growth in the bones of the spine can press on the spinal cord. The spinal cord has nerves that allow you to move and feel what happens to your body. Some of these nerves also control other functions such as bladder control.

Pressure on the spinal cord doesn't just cause pain; it also can damage the nerves in the spinal cord. This can lead to numbness and weakness, and may even cause paralysis. Most often this affects the legs, but if the tumor is pressing on the spinal cord in the neck, both the arms and the legs can be affected. Sometimes the first symptom you may have of spinal cord pressure is trouble urinating because nerves from the spinal cord control the bladder.

Symptoms from hypercalcemia

When cancer spreads to the bones, calcium from the bones can be released into the bloodstream. This can lead to high blood calcium levels (called hypercalcemia), which can cause problems such as constipation, nausea, loss of appetite, and extreme thirst. The high calcium causes you to make more urine, leading to dehydration. It can also make you feel very tired and weak. You may be sleepy or even confused. If not treated, hypercalcemia can even cause you to go into a coma.

Tell your doctor right away if you have symptoms

Many of the symptoms mentioned here can also be caused by something other than the spread of cancer to the bones. Still, it's very important for you to tell your doctors and nurses about any new symptoms such as these. Finding and treating bone metastasis early can help prevent problems later on.

Imaging tests to find bone metastases

Imaging tests use x-rays, magnetic fields, or radioactive substances to create pictures of the inside of the body. Imaging tests may be done for a number of reasons, including to help determine if cancer has spread to the bones. People who are suspected of having bone metastases often have one or more of these tests.

X-rays

Regular x-rays may show signs of the cancer's spread to the bones. X-rays are often among the first tests ordered if a person with cancer is having bone pain or other symptoms.

There are 2 types of bone metastases.

In osteolytic or lytic metastases, the cancer cells dissolve some of the minerals in the bone, making an area of the bone less dense. If the cancer has destroyed enough of the bone, these changes appear on x-rays as a darker hole in the gray-white bone image.

Osteoblastic or blastic metastases cause an area of the bone to appear denser or sclerotic. On x-rays, these metastases show up as spots that are whiter than the bone around them. This is seen more commonly in certain cancers, such as prostate cancer and some breast cancers.

Often, bone metastases have both lytic and blastic features.

X-rays can also show fractures (breaks) in bones that have been weakened by metastases.

Bone scan

This test can help show if a cancer has spread to bones. This test is useful because it shows the entire skeleton, so it can sometimes show bone metastasis that is not yet causing symptoms.

For a bone scan, a small amount of low-level radioactive material is injected into a vein (intravenously or IV). The substance settles in areas of damaged bone throughout the entire skeleton over the course of a couple of hours. You then lie on a table for about 30 minutes while a special camera detects the radioactivity and creates a picture of the skeleton.

Areas of active bone changes appear as "hot spots" on the skeleton because they attract radioactivity. These areas may suggest the presence of cancer, but other bone diseases can also cause the same pattern. To know exactly what is causing the hot spots, other imaging tests such as plain x-rays or MRI scans, or even a bone biopsy might be needed.

Bone scans can usually find metastases much earlier than regular x-rays. Bone scans can also be repeated over time to track how the metastases respond to treatments.

Sometimes bone scans fail to find cancer that has spread to the bones. This happens most often if the metastases are purely osteolytic (where bone is less dense). In some patients, the scan may show no radioactivity in areas of bone that the cancer has already destroyed.

Computed tomography (CT)

The CT scan is an x-ray test that produces detailed cross-sectional images of the body. Instead of taking one picture, like a regular x-ray, a CT scanner takes many pictures as it rotates around you. A computer then combines these pictures into images of slices of the part of your body being studied. A CT scan creates detailed images of both the bones and the soft tissues in the body.

Sometimes, a CT scan can help tell if the cancer has spread into your bones. It may be used when bone metastases are likely to be osteolytic, since these metastases sometimes don't show up in bone scans. CT scans are also good for judging the size and shape of a tumor in the bone and for assessing how stable a bone containing a tumor is.

Before the scan, you may be asked to drink 1 to 2 pints of a liquid called oral contrast. This helps outline the intestine so that certain areas are not mistaken for tumors. You may also receive an IV (intravenous) line through which a different kind of contrast dye (IV contrast) is injected. This helps better outline structures in your body. The injection may cause some flushing (a feeling of warmth, especially in the face). Some people are allergic and get hives. Rarely, more serious reactions like trouble breathing or low blood pressure can occur. Be sure to tell the doctor if you have any allergies or have ever had a reaction to any contrast material used for x-rays.

CT scans take longer than regular x-rays. You will need to lie still on a table while they are being done. During the test, the table slides in and out of the scanner, a ring-shaped machine that goes around the table. Some people feel a bit confined by the ring they move through while the pictures are being taken.

If a suspected area of bone metastasis is deep in the body, a CT scan is sometimes used to help get a sample of tissue. For this procedure, called a CT-guided needle biopsy, you stay on the CT scanning table while a radiologist guides the biopsy needle through your skin and toward the suspicious area. CT scans are repeated until the needle has reached the right place. A fine needle biopsy sample (tiny fragment of tissue) or a core needle biopsy sample (a thin cylinder of tissue) is then removed and looked at under a microscope.

Magnetic resonance imaging (MRI)

MRI scans use radio waves and strong magnets instead of x-rays. The energy from the radio waves is absorbed by the body and then released in a pattern formed by the type of body tissue and by certain diseases. A computer translates the pattern of radio waves given off by the tissues into a very detailed picture of parts of the body. Like a CT scan, MRI produces detailed cross-sectional slices of the body. Less often, a contrast material might also be used in MRI scans.

MRI scans may take up to an hour. For this test, you lie on a table that slides inside a long, narrow tube, which is confining and can be distressing for some people. Special open MRI machines can help with this, but the test still requires staying still for long periods of time. The machines also make buzzing and clicking noises that may be disturbing.

Because an MRI scan is very useful for looking at the spine and spinal cord, it is the standard test used if spinal cord compression is suspected. MRIs are also good at finding problems in bones and joints. Often an MRI scan is done to better define a bone mass seen on an x-ray. MRI scans can usually tell if the mass is likely to be a tumor, an infection, or some type of bone damage from other causes.

Positron emission tomography (PET)

For a PET scan, a form of radioactive sugar (known as fluorodeoxyglucose or FDG) is injected into the blood. The amount of radioactivity used is very low. Because cancer cells in the body grow quickly, they absorb large amounts of the sugar. After about an hour, you will lie on a table in the PET scanner for about 30 minutes while a special camera creates a picture of areas of radioactivity in the body. The picture is not finely detailed like a CT or MRI scan, but it provides helpful information about the whole body.

This test can sometimes find tumors that are too small to see on other imaging tests. PET scans look at the whole body at once, so they are sometimes used when your doctor thinks the cancer has spread but doesn't know where.

PET scans can give useful information, but they aren't very detailed. If an area on the scan looks like it could be cancer, other tests such as MRI or CT scans can be used to check it out further. Newer machines can combine PET and CT scans (PET/CT scanners) to give more detailed body images.

Lab tests to find bone metastases

Tumor markers

Some types of cancer release certain substances called tumor markers into the bloodstream. Patients with these types of cancer may have blood tests at regular intervals to see if levels of these markers are rising. An increase in tumor marker levels can mean that the cancer has spread, but it doesn't show where the cancer has spread. Other tests will be needed to show if the metastases are in the bone or if they are somewhere else in the body.

Prostate-specific antigen (PSA) is an example of a tumor marker. PSA levels are usually higher than normal in a man with prostate cancer, but they should become very low after treatment. If they start to rise again, it might suggest that the cancer has come back. If the levels are very high, it could mean the cancer has spread to the bones. More information about tumor markers can be found in our document called Tumor Markers.

Other blood tests

When cancer spreads to the bones, it may cause certain substances to be released into the blood that can be found by routine lab tests. For example:

• Calcium: Bone metastases can dissolve the bones, leading to a high blood calcium level.
• Alkaline phosphatase: When the bones dissolve, the levels of alkaline phosphatase may increase.

Newer types of blood tests are being studied that may be able to detect bone metastases earlier. (See the section, "What's new in bone metastasis research and treatment?" for more on this.)

Urine tests

Several substances can be released into urine when bone is damaged. One substance that can be measured is called N-telopeptide.

Biopsies used to find bone metastases

In most cases, cancer is diagnosed by removing a sample of body tissue and looking at it under a microscope. This procedure is called a biopsy.

If you have been diagnosed with cancer or have had cancer in the past, your doctor may be able to tell if you have bone metastasis based on the results of imaging tests such as a bone scan. If any of your blood test results also suggest bone metastasis, this makes the diagnosis even more certain. When this is the case, your doctor might not need to get a tissue sample. But if it is not clear if the cancer has spread to the bones based on imaging and other tests, your doctor may need to take a sample from an abnormal area to find out if it is cancer.

Needle biopsy

There are 2 main types of needle biopsies.

Fine needle biopsy or aspiration: With fine needle aspiration (FNA), a very thin, hollow needle is used to take a small amount of fluid and small tissue fragments from the tumor. The biopsy is done after numbing the area. It may be uncomfortable, but is not usually painful.

If the suspicious area can be seen or felt near the surface of the body, the doctor can aim the needle right into the area. If the suspicious area cannot be felt or seen because it is deep inside the body, the doctor may use CT scans to guide the needle. This is called a CT-guided needle biopsy. Sometimes, ultrasound may be used to aim the needle instead of CT.

It can be hard to get a fine needle into a bone, so this type of biopsy is done only if the bone is weakened or if the cancer has spread into the soft tissue around the bone.

Core needle biopsy: This type of biopsy is much like FNA except it uses a larger needle. The needles used for a core biopsy remove a small cylinder of tissue.

Surgical bone biopsy

Sometimes needle biopsies don't provide an answer, and a surgical biopsy is needed. In this procedure, the surgeon cuts into the bone to remove a small part of the tumor. This is also called an incisional biopsy. It is rarely needed to diagnose bone metastases.