Diagnosis of a Bone Metastasis
When a person is first diagnosed with cancer, laboratory tests and imaging tests may be performed to determine if the cancer has spread to the bones or any other organs. After these tests, if the doctor is still uncertain about whether the cancer has spread to the bones, a biopsy may be required to confirm the diagnosis.
Imaging Tests
X-rays, bone scans, CT scans, MRI scans and PET scans may be used to detect cancer metastases in the bones, determine the extent of the disease and monitor the patient’s response to treatment.
X-Ray
An X-ray can reveal weakened areas of bone, areas of increased bone density and fractures in the bones. Many times, a simple X-ray of the affected area may be able to show if the cancer has spread to the bone. X-rays are not used to screen for bone metastases, but may be recommended to look at a specific area causing pain, or to further examine abnormal areas found on a bone scan.
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Bone Scan
A bone scan provides a picture of all the bones in the body at once and allows the doctors to detect small areas of cancer cells not visible on standard X-rays. A radioactive tracer that is attracted to areas of increased bone activity is injected intravenously. This tracer collects in areas of bone that have been damaged by cancer, and are currently growing and healing. Bone scans are very sensitive, meaning they are very accurate and show any suspicious areas in the bones. However, bone scans may also detect benign bone conditions related to other diseases, and other tests such as a CT scan, MRI scan or biopsy may be needed to confirm the diagnosis.
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Computed Tomography (CT) Scan
A CT scan takes many pictures as it rotates around the body. It produces detailed cross-sectional images of the body and can detect cancer in the bones, as well as the size and shape of the tumor. A CT scan may be recommended to look at any suspicious areas found on a bone scan and/or X-ray in more detail. CT scans are especially useful for evaluating cancer that has spread to the ribs.
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Magnetic Resonance Imaging (MRI) Scan
An MRI scan uses radio waves and a strong magnet to create clear and detailed images of body parts. Radio waves are absorbed by the body and then released in a certain pattern, which is translated by a computer in order to show “slices” of the body. MRI scans are very accurate and are especially useful for examining the soft tissues of the body. An MRI scan may be performed if the doctor thinks that cancer has spread to the spinal cord, or if the doctor is unable to confirm a bone metastasis with a X-ray, bone scan or other imaging tests. MRI scans can reveal how much bone has been destroyed.
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Positron Emission Tomography (PET) Scan
For a PET scan, the doctor injects a radioactive substance into the patient's bloodstream. This substance collects in malignant (cancerous) cells in the patient's body. The doctor then uses a PET scanner to detect these areas of radioactivity and to find the exact location of cancer in the patient's body. If any suspicious areas are detected on a PET scan, a more detailed test like a CT scan or MRI scan may be recommended.
Laboratory Tests
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Laboratory tests may be performed to test the blood and urine for substances that are released into the body when cancer spreads to the bones. A blood chemistry profile measures the levels of different substances in the blood, such as protein, creatinine, calcium, and blood urea nitrogen (BUN). The doctor will look at the level of calcium in the blood to check for hypercalcemia. The doctor may also check the levels of alkaline phosphatase (ALP) and lactate dehydrogenase (LDH) in the blood, which can rise when cancer spreads to the bones. The doctor may test the levels of N-telopeptide in the urine. Too much N-telopeptide may indicate a bone disease or metastatic cancer. Blood and Urine Protein Electrophoresis are tests that detect Multiple Myeloma proteins in the blood and urine, and may be recommended to rule out Multiple Myeloma.
Biopsy
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A bone biopsy may be required if the doctor is still unclear about whether the cancer has spread to the bones after imaging tests and laboratory tests. If any suspicious areas are found on these tests, a small tissue sample will be removed from the bone and examined under a microscope to determine if it is cancerous. A biopsy is the only way to know for sure if cancer is present. A CT scan may be used to guide the biopsy needle to the suspicious area.
