People with cancer have special risks as it relates to their bones. Healthy bone is constantly being broken down and then built back up. This process is called bone remodeling. When your bone is broken down, nutrients in the bone are released. Unfortunately, these nutrients can promote cancer cells to grow and thrive. Cancer cells are attracted to this nutrient-rich environment and settle into the bone and grow. The cancer cells themselves can release substances that increase the amount of bone that is broken down, creating a vicious cycle that leads to weakening of the bone and tumor growth. When the cancer cells grow and divide in the bone, they form tumor deposits called metastases. Even though there can be tumors that start in the bone (primary bone tumors), most tumor deposits in the bone are the result of cells travelling through the blood to the bone (secondary bone tumors). Bone is the third most common site of distant cancer recurrence. Because the cancer cells have traveled with circulating blood, it is more common to have multiple tumors in different bones than only one site of cancer in a single bone. Complications of Bone Metastases The most common cancers that spread to the bone causing bone metastases include breast cancer, prostate cancer, lung cancer, kidney cancer, and thyroid cancer. When the cancer cells form tumors in the bone, the bone metastases can cause a variety of problems, including: Pain from structural damage to the bone Release of high amounts of calcium into the circulation, causing a condition called hypercalcemia. High calcium levels in the blood can lead to nausea, vomiting, and even confusion. Destruction of the structure of the bone, increasing the risk for breaks or fractures Treating Bone Metastases Bone metastases are often treated by two complementary approaches: The first approach is to treat the cancer itself by using medications such as chemotherapy or anti-hormone therapies. The goal of this treatment is to shrink the cancer and stop it from growing. Which treatment is used depends on the specific type of cancer that has spread to the bone. For example, breast cancer that has spread to the bone will be treated by medicines effective at treating breast cancer. The second approach will be to target the bone itself. Medicines such as denosumab (Xgeva) or zoledronic acid (Zometa) decrease the body's ability to break the bone down to release nutrients. They strengthen the bone and lower the risk of the bone breaking. Other therapies may be used as needed to control symptoms of cancer in the bone, such as: Radiation therapy to treat pain and prevent fracture Surgery to repair fracture Medications, including steroids and Zoledronic acid (Zometa and Reclast), to lower elevated calcium levels As the cancer is controlled, most symptoms caused by the cancer in the bone improve. Many patients will not have symptoms from having cancer in the bone. Ask your doctor if you need to limit or change your activities to prevent the fracture of bones affected by cancer. Marjorie Green, MD, is an oncologist specializing in breast cancer. Dr. Green practices at MD Anderson Cancer Center in Houston, Texas. She is a HealthGrades Recognized Doctor.