Metastatic Bone Tumor Fundamentals
Many tumors that originate in an organ, such as breast, prostate, colon, liver, kidney, lung, thyroid gland, ovary, or skin can spread to bone. Breast cancer and prostate cancer are the most common tumors to spread to bone. Other tumors may arise directly in the bone marrow and cause similar problems, such as myeloma or lymphoma.
What are the symptoms?
A tumor can cause bone to be destroyed and weakened to the extent that it breaks. Fractures can occur even while doing something as simple as getting out of a chair or rolling over in bed. This can be a serious problem, resulting in pain, loss of blood, and loss of mobility. Urgent surgery is often necessary. Therefore, it is very important to try to prevent these fractures. The major symptom is bone pain especially with mechanical stress, such as walking of lifting.
Patients with known cancers that can spread to the bone may be screened using X-rays or bone scans to identify any areas where fracture might occur. These areas are then closely observed for signs of breakage.
About 75% of patients who have a "pathologic fracture" (i.e. a fracture which resulted from a weakness in bone caused by a disease), recognize that they had increased pain (above and beyond their existing deep, boring pain) at the site of the fracture for one to a few days prior to the fracture. Therefore, individuals who have a known tumor that might spread to the bone are strongly encouraged to contact their physician for any new pain that seems to increase over more than two to three days. Patients with metastatic tumors from breast cancer, renal cancer, and lung cancer are particularly prone to pathologic fractures, since these tumors tend to cause the most bone destruction. Breast cancer alone accounts for about 60% of all pathologic fractures.
What are the treatments?
When there is pain, but the amount of bone destruction is not severe enough to make a fracture inevitable, your doctor may prescribe radiation therapy to control the tumor. This is usually done over a period of several sessions. The dose and technique depend strongly on the type of tumor and the location. Some metastatic tumors are very sensitive to radiation. Others are less sensitive.
It is almost always necessary to protect the weakened area of bone from stress for a period of six to 12 weeks around the time of radiation. If radiation is effective, the tumor cells die. This results temporarily in increased weakness at the site of the tumor until the dead tumor tissue is replaced with healing bone or scar tissue, which reduce the chance of fracture. This protection can involve the use of a sling or protective brace for an arm. If the area is in the leg, use of crutches, a walker, or even a wheelchair may be necessary.
One of the most effective means of reducing the risk of fractures and pain related to bone metastasis is the use of bisphosphonate inhibitors of bone resorption. Medications such as Palmidronate (Aredia) and Etidronate (Zometa) have been shown to significantly reduce the risks of bone complications resulting from metastasis, particularly in breast cancer and myeloma, by inhibiting the bone destruction caused by the tumor. These medications are appropriately prescribed by medical oncologists as part of an overall treatment plan.
The most dangerous areas for fracture are regions where more than half of the bone has been lost. Most often, these sites require surgery to remove the tumor or support the area, or a fracture will occur. Though most patients would like to avoid surgery, it is far safer and more comfortable for the individual to have an elective procedure to prevent a fracture than to be forced to have urgent surgery following a fracture that may occur by surprise. The ability to preserve function is more likely if treatment is initiated before a fracture.
Surgery is performed with the goal of returning the individual to a state of comfort and mobility as soon as possible. Though few individuals who present with a bone metastasis or a fracture through a bone metastasis can be cured from their tumor, the vast majority return to productive life for an extended period of time. Over half of all individuals presenting with a pathologic fracture continue to live with their cancer for more than two years, and sometimes more than 12 years. As a result, surgical reconstruction in this setting needs to be planned to provide long-term function and stability as well as long-term control of tumor cells at the site being treated.