The staging of a cancer refers to determining the extent of the disease. Once a prostate cancer is diagnosed on a biopsy, additional tests are done to assess whether the cancer has spread beyond the gland. For this assessment, biopsies of the surrounding organs, such as the rectum or urinary bladder, or of the nearby (pelvic) lymph nodes might be done. In addition, imaging tests are usually performed. For example, radionuclide bone scans can determine if there is a spread of the tumor to the bones. Additionally, CAT scans (coaxial tomography) and MRIs (magnetic resonance imaging) can determine if the cancer has spread to adjacent tissues or organs such as the bladder or rectum or to other parts of the body such as the liver or lungs. Newer scanning using a method called PET scan can sometimes help to detect hidden locations of cancer that has spread to various areas of the body.