Diagnosis

When a patient experiences symptoms suggestive of bone metastasis, various tests can be done to confirm the cause. In some cases bone metastasis may be detected before symptoms arise.

X-rays. Radiographic examination, or X-rays, can provide information about what part of the skeleton the cancer has spread to as well as the general size and shape of the tumor or tumors. (It is common for more than one metastasis to be found.)

Bone scan. Bone scans can detect bone metastasis earlier than X-rays can. They also allow the doctor to monitor the health of all the bones in the body, including how they are responding to treatment.

In a bone scan, the patient is given an injection of a low amount of radioactive material (much lower than that used in radiation therapy). The radioactive substance is attracted to diseased bone cells throughout the body. Diseased bone appears on the bone scan image as darker, dense areas. Conditions other than metastasis, such as arthritis, infections, or previous fractures that have healed, may also be picked up on a bone scan, although the patterns they produce are often different from those produced by cancer. Additional tests can help distinguish among these other conditions.

Computed Tomography (CT) scan. The CT scan provides X-ray images to look at cross sections of organs and bones in the body. Rather than provide one image as a conventional X-ray does, the CT scanner takes many pictures as it rotates around the body. A computer combines the images into one picture to show if cancer has spread to the bones. It is particularly helpful in showing osteolytic metastases that may be missed with the bone scan.

Magnetic Resonance Imaging (MRI). MRI scans use radio waves and strong magnets instead of X-rays to provide pictures of bones and tissues. They are particularly useful in looking at the spine.

Laboratory tests. Bone metastasis can cause a number of substances, such as calcium and an enzyme called alkaline phosphatase, to be released into the blood in amounts that are higher than normal. Blood tests for these substances can help diagnose bone metastasis. Doctors also can measure the levels of these chemicals over time to monitor a patient's response to treatment. Elevated levels of these substances can indicate other medical conditions besides metastasis.

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