Cancer is a serious, chronic medical condition characterized by the unregulated division of cells in localized areas of the body, resulting in tumors which have the potential to create fatal complications. While researchers have been unable to definitively specify the exact cause of cancer, there are many known risk factors. These include poor diet, tobacco use, exposure to radiation and environmental contaminants, inactivity and genetics. There are more than 200 different types of cancer which occur in human beings, with advancing age being associated with increased risk. Various therapies are used to treat cancer, including surgery, chemotherapy and radiation treatments, and survival rates depend on the type of cancer, the health of the patient, and the extent to which the cancer has spread at the time of diagnosis.