Metastatic brain tumors result from cancer that started elsewhere in the body and spread (metastasized) to the brain. For example, if lung cancer has spread to the brain, the cells in the tumor would look like lung cells rather than brain cells. Metastases to the brain are the most common intracranial tumors in adults, 10 times more common than primary brain tumors. These tumors can be treated with surgery, whole brain radiation therapy or focus Gamma Knife Radiosurgery.