When cancer is diagnosed, staging tests help determine how extensive the cancer is in terms of its location, size, growth into nearby structures, and spread to other parts of the body. People with cancer sometimes become impatient and anxious during staging tests, wishing for a prompt start of treatment. However, staging allows doctors to determine the most appropriate treatment as well as helping to determine prognosis.
Staging may use scans or other imaging tests, such as x-ray, CT, MRI, bone scintigraphy, or positron emission tomography (PET). The choice of staging test(s) depends on the type of cancer, as different cancers involve different parts of the body. CT scanning is used to detect cancer in many parts of the body, including the brain and lungs and parts of the abdomen, including the adrenal glands, lymph nodes, liver, and spleen. MRI is of particular value in detecting cancers of the brain, bone, and spinal cord.
Biopsies are often needed for staging and can sometimes be done together with the initial surgical treatment of a cancer. For example, during a laparotomy (an abdominal operation) to remove colon cancer, a surgeon removes nearby lymph nodes to check for spread of the cancer. During surgery for breast cancer, the surgeon biopsies or removes lymph nodes located in the armpit to determine whether the breast cancer has spread there; this information along with features of the primary tumor helps the doctor determine whether further treatment is needed. When staging is based only on initial biopsy results, physical examination, and imaging, the stage is referred to as clinical. When the doctor uses results of a surgical procedure or additional biopsies, the stage is referred to as pathologic. The clinical and pathologic stage may differ
In addition to imaging tests, doctors often obtain blood tests to see if the cancer has begun to affect the liver, bone, or kidneys.