Staging is the process of testing that evaluates your pet's cancer with regard to tumor size and spread (if the cancer has metastasized or involves other parts of the body). From the information obtained with these tests, a numeric description is given with higher numbers indicating more advanced disease (i.e. stage V is more advanced than stage I). Knowing the stage of your pet's cancer is critical in selecting the proper treatment as well as in establishing their prognosis. The numeric stage is based on initial testing. Therefore, it will not change during the course of your pets therapy. The grade of a cancer is different then it's stage. Grading requires a tumor biopsy and microscopic description. Staging on the other hand utilizes testing such as radiographs, blood analysis, bone marrow analysis and others based on the known behavior of the tumor and changes found in your pet. The information obtained though testing reveals critical information regarding the cancer behavior and also allows your veterinarian to assess your pets overall health. Depending on the needs of your pet, these tests may occasionally be repeated to determine if a response to treatment has occurred.