Bones are common sites for metastases, which occur when cancer cells from a primary cancer tumor relocate to the bone. Prostate, breast, and lung cancers are among the most common cancers that spread to the bone, but metastases are possible with other cancers. Primary bone cancers – those in which the primary tumor starts in the bone – are rare. Therefore, bone cancer and bone metastases are not the same.
Metastases can cause small holes, known as osteolytic lesions or lytic lesions, to develop in the affected bone. These lesions can weaken bones and increase the risk of fractures or other problems.
What are the symptoms?
Bone metastases can be painful at or near the site of the metastasis, which is usually the first symptom that patients notice. Patients describe the pain as gradually increasing over time and becoming more severe. Patients with spinal cord metastases often experience pain or discomfort that is worse at night or with bed rest. Patients with lesions involving longer bones like the arms and legs often have pain with activity or movement.
If the metastasis forms in the spinal area, it can compress the spinal cord and lead to back pain or difficulty walking.
Other symptoms might include numbness and weakness in the legs, problems with the bowels or bladder or numbness in the abdominal area. For patients who receive extensive chemotherapy or radiation therapy, bone metastases can affect the bone marrow and lead to anemia, a lower than normal level of red blood cells. Symptoms of anemia include fatigue, weakness and shortness of breath. Patients whose white blood cells are affected might be more susceptible to infections, which could cause fever, chills, fatigue or pain. Some patients suffer from lower platelet counts, which can lead to abnormal bleeding. The symptoms vary depending upon the type of blood cell affected.
What are the treatment options?
Bone metastases can be treated with surgery, external beam radiation therapy, radiopharmaceutical therapy and stereotactic radiosurgery.
In most bone metastases cases, surgery can restore the bone’s original function. Depending on the tumor location and size, open surgery allows doctors to remove all or part of the tumor and stabilize the bone to prevent fractures. With fractures or impending fractures, surgery could include placing metal plates, rods, screws, wires, pins or prostheses. These procedures can help strengthen or provide structure to the bone. Surgery also can be used to reconstruct damaged bone or joints with metal, plastic, transplants or a combination of materials. Over time, the reconstruction material becomes part of the human skeleton.
Some patients may experience pain or limited physical activity for a period of time after surgery. Although there are many surgical options for bone metastases, most patients do not need surgery.
External-beam radiation therapy
Patients treated with external-beam radiation therapy receive a certain number of daily radiation treatments over a period of one to two weeks and typically no more than three weeks in most circumstances. This type of therapy is referred to as three-dimensional conformal or intensity-modulated radiation therapy. IMRT, as it’s known, allows doctors to customize the radiation beams to individual patients, resulting in much better targeting than with conventional radiation.
External-beam radiation therapy uses high-energy radiation beams to injure or destroy cancer cells in the area of the bone metastasis or tumor. Although some normal non-cancer cells are destroyed in the process, these cells can usually repair themselves and resume normal function. Benefits of radiation therapy include reduced bone pain and lower risk of fractures.
With radiopharmaceutical therapy, radioactive metals are injected into the body to target and destroy cancer cells. The procedure can decrease pain or relieve it entirely. Radiopharmaceutical therapy has been shown to decrease platelet and white blood cell production in some patients as they undergo more treatments.
Radiosurgery is a non-surgical option for treating bone metastases and delivers targeted high-dose radiation to cancer cells while minimizing exposure to healthy tissue. Treatment is delivered in one to five sessions and no overnight hospital stay is required. Recovery time with radiosurgery is much shorter than standard surgery, and treating more than one metastasis is typically easier with radiosurgery than conventional surgery. While healthy tissue can be damaged with conventional radiation therapy for bone metastases, radiosurgery with CyberKnife spares normal tissue, which is particularly important when treating spinal metastases close to a critical structure, such as the spinal cord. Radiosurgery has been shown to control tumor growth and provide pain relief.