The primary site is the origin of cancer. In a particular patient, it may be cancer originating in the breast, lung, intestines, kidney, skin or other sites. The relative travel from the primary site to the bone is usually the blood stream, although some times adjacent erosion of the bone may occur from a primary tumor. The second possibility is less frequent in occurrence.
Bone metastases are worrisome for several reasons.
The first is they may cause pain that is sometimes intractable or produce a need to take pain medicines that have significant side effects. Furthermore, bone metastases may occur in bones responsible for bearing weight such as the spine, pelvis or long bones of the legs. These bones may snap under such duress creating further pain and immobility. For the vast majority of patients with bone metastases, radiation offers an excellent method of palliation. Generally, radiation will kill the cancer cells within the area of concern, allowing the normal bone to heal.