Cancers that begin elsewhere in the body may spread (metastasize) to the bones.
In particular, cancers of the breast, lung, prostate gland, kidney, thyroid gland, and colon may metastasize to the bones.
The main symptom is bone pain.
An imaging test, such as x-rays, magnetic resonance imaging (MRI) or computed tomography, may show the bone abnormality, or a sample of tissue may need to be removed and tested (biopsy).
Radiation therapy, chemotherapy, or surgery may be done depending on the type of cancer that has spread.
Metastatic bone tumors are cancers that have spread to the bones from their original (primary) site elsewhere in the body (see Development and Spread of Cancer).
Cancers most likely to spread to the bones include those that start in the following areas:
Breast cancer is the most common cancer to spread to bone. However, any cancer may eventually spread to bone. Cancer may spread to any bone, although cancers do not commonly spread to bone below the mid forearm or mid calf.
Metastatic bone tumors cause bone pain, but they may not cause any symptoms for some time. The pain can be severe. Pain may occur when at rest or at night and tends to progressively worsen.
Cancerous tumors gradually weaken a bone. The weakness makes it much easier for the bone to break (fracture) while doing routine activities (called a pathologic fracture).
A person who has or has had cancer and develops bone pain or swelling is evaluated by a doctor for metastatic bone tumors.
To evaluate a single area of bone, other imaging tests such as magnetic resonance imaging (MRI), computed tomography (CT), or positron emission tomography (PET) is done. PET is usually combined with computed tomography (PET-CT) when used to evaluate tumors.
Occasionally, a metastatic bone tumor causes symptoms before the original cancer has been detected. Symptoms may be bone pain (particularly pain that affects more than one area because of multiple tumors) or a fracture where the tumor has weakened the bone (a pathologic fracture). In these situations, a biopsy is done and usually gives clues as to the location of the original cancer, because the type of cancer tissue can often be recognized under the microscope. This information can direct the doctor to where the original cancer started (for example, in the lungs, breasts, prostate, kidneys, thyroid, or colon).
Once a metastatic bone tumor is diagnosed, doctors do other tests to determine where the original cancer started. For example, a chest x-ray or chest CT scan may be done to look for tumors in the lungs, or mammography may be done to look for tumors in the breasts.
Treatment of metastatic bone tumors depends on the type of cancer that has spread to the bone. Some types respond to chemotherapy, some to radiation therapy, some to both, and some to neither. Radiation therapy is usually most effective.
Surgery to stabilize the bone is often done to treat fractures and sometimes even to prevent fractures. Surgery for pathologic fractures may involve placing a rod inside the bone, using plates and screws to stabilize the bone, or removing the affected bone and rebuilding the limb and joint.
When the original (primary) cancer has been removed and only a single tumor remains in the bone, especially if the tumor developed years after the original tumor, the single tumor is surgically removed and the bone is rebuilt. Sometimes this removal and rebuilding is combined with radiation therapy, chemotherapy, or both. This combination of treatment rarely cures the cancer but may significantly improve the person's quality of life as well as the function or appearance of the limb.
One of the goals of treatment is to minimize the loss of bone tissue and relieve pain.
Loss of bone tissue can cause pain and make bones tend to fracture, which can require surgery. Bone loss can be minimized by using radiation therapy and drugs that prevent bone loss (such as bisphosphonates or denosumab) before bone loss is widespread and pain occurs.
To relieve spine pain, kyphoplasty or vertebroplasty may be done. Either procedure can be done if tumors are causing the back bone to collapse but are not putting pressure on the spinal cord. In kyphoplasty, a balloon is inserted into the back bone and is expanded to restore the bone to its normal shape and prevent the bone from collapsing further. Then bone cement (methyl methacrylate) is injected. Vertebroplasty is similar to kyphoplasty except that no balloon is inserted. If the tumors are at risk of causing collapse that could put pressure on the spinal cord and cause spinal cord damage (such as weakness or paralysis of the legs), treatment, such as surgery, to reduce the pressure and stabilize the spine may be recommended.