Staging is done at. Diagnosis to determine this. The tumor arises in an organ, we search for its local extent, involvement of nodes, or travel to distant organs. This varies with each organ and tumor type.
Doctors will measure. Before treatment is started, doctors do a variety of tests to determine if your cancer is localized or has spread to other places in the body. Using blood test, x-rays, ct scans, MRI and pet scans (not necessarily all of these for each patient) they will stage the cancer using very specific criteria established for every type of cancer. This helps your doctor determine treatment and prognosis.