Colorectal cancer staging

Editor(s)-in-Chief: C. Michael Gibson, M.S.,M.D. [mailto:mgibson@perfuse.org] Phone:617-632-7753; Elliot B. Tapper, M.D., Beth Israel Deaconess Medical Center

Staging
Colon cancer staging is an estimate of the amount of penetration of a particular cancer. It is performed for diagnostic and research purposes, and to determine the best method of treatment. The systems for staging colorectal cancers largely depend on the extent of local invasion, the degree of lymph node involvement and whether there is distant metastasis.

Definitive staging can only be done after surgery has been performed and pathology reports reviewed. An exception to this principle would be after a colonoscopic polypectomy of a malignant pedunculated polyp with minimal invasion. Preoperative staging of rectal cancers may be done with endoscopic ultrasound. Adjuncts to staging of metastasis include Abdominal Ultrasound, CT, PET Scanning, and other imaging studies.

Dukes' system
Dukes' classification, first proposed by Dr Cuthbert E. Dukes in 1932, identifies the stages as:
 * A - Tumour confined to the intestinal wall
 * B - Tumour invading through the intestinal wall
 * C - With lymph node(s) involvement
 * D - With distant metastasis

TNM system
The most common current staging system is the TNM (for tumors/nodes/metastases) system, though many doctors still use the older Dukes system. The TNM system assigns a number :
 * T - The degree of invasion of the intestinal wall
 * T0 - no evidence of tumor
 * Tis- cancer in situ (tumor present, but no invasion)
 * T1 - invasion through submucosa into lamina propria (basement membrane invaded)
 * T2 - invasion into the muscularis propria (i.e. proper muscle of the bowel wall)
 * T3 - invasion through the subserosa
 * T4 - invasion of surrounding structures (e.g. bladder) or with tumour cells on the free external surface of the bowel
 * N - the degree of lymphatic node involvement
 * N0 - no lymph nodes involved
 * N1 - one to three nodes involved
 * N2 - four or more nodes involved
 * M - the degree of metastasis
 * M0 - no metastasis
 * M1 - metastasis present

AJCC stage groupings
The stage of a cancer is usually quoted as a number I, II, III, IV derived from the TNM value grouped by prognosis; a higher number indicates a more advanced cancer and likely a worse outcome.
 * Stage 0
 * Tis, N0, M0
 * Stage I
 * T1, N0, M0
 * T2, N0, M0
 * Stage IIA
 * T3, N0, M0
 * Stage IIB
 * T4, N0, M0
 * Stage IIIA
 * T1, N1, M0
 * T2, N1, M0
 * Stage IIIB
 * T3, N1, M0
 * T4, N1, M0
 * Stage IIIC
 * Any T, N2, M0
 * Stage IV
 * Any T, Any N, M1