Bone metastasis occurs when cancer cells break away from their primary tumor, spread throughout the body, and invade a bone. Bone is one of the most common sites for cancer to metastasize, along with lungs and liver. It is important to note that cancer that has metastasized to the bones is still considered to be the same type of cancer that it started out as, and not “bone cancer” per se. For example, if lung cancer metastasizes to the bones, it is still called lung cancer and not “bone cancer.”
When metastatic tumor cells invade the bone, they initiate a complex interaction with bone-resident cells that results in abnormal bone function. These changes are associated with a number of adverse clinical symptoms, including pain, fractures, and the development of excess calcium in the blood (hypercalcemia). These processes are influenced by both tumor characteristics and the receptive bone microenvironment that is present at frequent sites of metastasis such as the vertebrae, ribs, pelvic bones, and ends of long bones.
The bone is a unique organ in the body, not only because it provides structural support but also because it integrates and responds to many different systemic physiologic signals. As a result, the bone is a dynamic structure that can be affected by a wide variety of diseases and can change with age.
Most cancers that spread to the bone cause a variety of signs and symptoms, including bone pain and fractures, spinal cord compression, hypercalcemia, and other skeletal-related events (SREs). Although most bone metastases are not curable, prompt diagnosis and treatment can help prevent SREs and reduce symptom severity.
In some cases, the care team may recommend radiation therapy to destroy cancer cells and decrease bone pain. The most commonly used technique for MBD is local field radiation, which directs the beam directly at the metastatic lesion and the immediate surrounding bone tissue. Occasionally, the care team may recommend a more extensive approach, known as hemibody irradiation, which uses large-field radiation to target larger areas of the upper, midsection, or lower body rather than individual bones.
Other treatments for MBD include the use of medications to strengthen bones and reduce pain. These medications are typically given intravenously or orally and can be combined with chemotherapy to provide added benefits for patients.
Survival rates for cancer that spreads to the bone vary greatly by the specific type of cancer, the location in the bone, and the patient’s general health condition and the type and duration of their treatment for the original tumor. These statistics are averages based on data from large groups of patients and cannot be applied to an individual patient. It is important for people with bone metastasis to discuss their personal situation with their doctor and family members.