What are the stages of cancer?

Conditions Expert Dr. Otis Brawley Chief Medical Officer,
American Cancer Society

Expert answer

In cancer medicine, staging is an assessment of spread of disease. Knowing the stage of the disease helps plan a treatment and determine the likely outcome and course course of disease.

Staging rules are determined by the American Joint Committee on Cancer (AJCC) and the Union for International Cancer Control (UICC). More detailed information can be found at the AJCC website.

Staging is based on knowledge of the way cancer develops. Some staging systems cover many types of cancer; others focus on a particular type. For most cancers, the stage is based on three main factors:

• What is the organ in which the original cancer started

• What is the size of the original tumor

• Has the cancer spread to surrounding lymph nodes

• Has the cancer spread to distant areas of the body

Information from the physical examination, medical imaging tests (such as X-rays, CT scans, and MRI scans) as well as laboratory tests are used to determine a "clinical stage." Surgical removal of the tumor allows for further assessment of the primary cancer and the areas of possible spread. This can result in a "pathologic stage." The pathologic stage, when available, is more accurate.

Given this information for most cancers, the physician will determine a TNM stage. The TNM staging system is based on the extent of the tumor (T1 to T4), the extent of spread to the lymph nodes (N0 to N3), and the presence of metastasis (M0 to M1). Once the T, N, and M are determined, they are combined, and an overall "stage" of I, II, III, IV is assigned. Sometimes these stages are subdivided as well, using letters such as IIIA and IIIB.

Leukemia, myeloma and brain tumors are usually staged differently.

Most cancers are staged from stage I which is localized or confined to the area where the malignancy started to stage IV, which means the cancer has spread far from its origin, usually to involve distant organs.

Stage helps determine the prognosis of the cancer. In general stage I has more successful outcomes than stage II, stage II is better prognosis than stage III, etc. In some diseases, there are subsets of stage indicated by a letter. stage IIB breast cancer is more advanced than stage IIA for example.

There are slight differences in the staging system for every type of cancer, so letters and numbers do not always mean the same thing for every kind of cancer. In some cancer types, additional factors are used to stage the disease.

In prostate cancer, the Gleason score (a microscopic grading of tumor aggressiveness) is used. In lymphoma (cancer of the lymphatic system), part of the staging includes whether or not some constitutional symptoms are present. These symptoms are fever, night sweats, or unexplained weight loss.

Stage also helps determine the most appropriate treatment for the cancer. Stage I and II cancers are most commonly treated with localized therapy such as surgery or radiation, but for certain cancers chemotherapy can be added. Stage III diseases are more commonly treated with radiation and chemotherapy, but in select patients with certain cancers can be treated with surgery.

Other elements determining appropriate treatment and prognosis include the kind of cancer and the overall health status of the patient. A stage III colon cancer in an otherwise healthy patient will most likely be treated with surgical removal of the effected part of the colon and a chemotherapy regimen specific to colon cancer given after the surgery. Someone with a stage III cancer of the throat may be reasonably treated with a chemotherapy regimen specific to head and neck cancer and radiation given during the course of the chemotherapy.

Next week: The staging and treatment of lymphoma.