Bone metastasis, also known as bone mets, is cancer that has metastasized, or spread, to the bones from its primary site in another part of the body. Bone metastasis is a different condition than primary bone cancer, in which the cancer actually originates in the bone. This condition is, in fact, much more frequently seen than primary bone cancer. Bones are a common site of metastasis for many kinds of tumors, including breast, lung, and prostate cancers.
Metastasis typically occurs when cancer cells from a primary tumor break away and travel into the bloodstream, metastasizing or forming a secondary tumor in another part of the body. When the secondary tumor is formed in a bone, it can cause damage through a process known as osteolysis. This process causes small holes, called osteolytic or lytic lesions, to be formed in the bones. Lytic lesions cause pain and make the bones weaker, increasing the risk of fractures.
Another primary symptom of bone metastasis, in addition to fractures, is bone pain. This is the most common symptom and is most often felt first at the site of metastasis. Patients with bone metastasis may feel pain begin gradually and increase over time. When metastasis occurs in the longer bones of the arms or legs, the pain is usually made worse by physical activity.
Other symptoms of bone metastasis may be related to spinal cord compression, if the secondary tumor is located in the spinal area. These may include back pain, difficulty with walking, numbness or weakness in the legs or abdominal area, or trouble with the bowels or bladder. Patients with bone metastasis to the spinal area may feel more pain with bed rest.
Bone metastasis is most often diagnosed using x-rays, as lytic lesions typically appear as dark spots on the images. The location, as well as the basic size and shape of a tumor, can also be seen using x-rays. Computed tomography (CT) scans can also be used in conjunction with x-rays to provide more detailed information about the exact location and dimensions of the tumor. Magnetic resonance imaging (MRI) may be an additional diagnostic tool. If the patient is experiencing bone pain, but has normal x-rays and CT scans, an MRI can be more successful at showing changes in the bone marrow.
There are several treatment options for bone metastasis, including chemotherapy, radiation therapy, and surgery to restore function of the diseased bone. Bisphosphonates are a type of medication given intravenously to help decrease the risk of fractures and pain associated with the condition. Other medications are also used in the management of pain in these cancer patients.