Cancers from one location of the body can spread and invade other areas of the body. If a tumor spreads to the bone, the cancer can cause pain. Initially, pain can be relieved with opioid or non-steroidal inflammatory medication.  However, when cancer grows, the pain can be severe that high doses of opioid pain medication cannot provide palliative relief.  Palliative radiotherapy to spine or extra-axial skeleton is one way of treating skeletal metastasis to help reduce the pain. Additionally, treating bony metastasis can prevent or delay fractures of the bony metastatic disease.