Cancer staging is a testing process that determines how much cancer is present in the body and how far it has spread. Cancer staging helps your doctor determine the appropriate plan of care and estimate your prognosis. Staging takes place as soon as cancer is found, and includes evaluating the site of the tumor, cancer type, tumor size or extent, number of tumors and the tumor grade. Cancer staging is determined through physical exams, imaging studies (MRI, X-rays, PET scans), laboratory tests, pathology reports and surgical reports. After your treatment is complete, your doctor will reassess your cancer in the restaging period. This will determine if your treatment was successful and allow your doctor to create a new plan of care.