Colorectal cancer staging

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Elliot B. Tapper, M.D., Saarah T. Alkhairy, M.D.

Overview

Colorectal cancer staging is an estimate of the amount of penetration of the 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. The staging systems are called Duke's classification, TMN classification, and AJCC stage grouping.

Colorectal Cancer Staging

Colorectal cancer staging is an estimate of the amount of penetration of the 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 have been 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 Classification 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 Classification System

Main article: TNM

The most common current staging system is the TNM classification (tumors/nodes/metastases) system, though many doctors still use the older Dukes system. The TNM classification system assigns a number:

Stage	TNM Value
0	Tis, N0, M0
I	T1, N0, M0; T2, N0, M0
IIA	T3, N0, M0
IIB	T4, N0, M0
IIIA	T1, N1, M0; T2, N1, M0
IIIB	T3, N1, M0; T4, N1, M0
IIIC	Any T, N2, M0
IV	Any T, Any N, M1

• 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

Grades of Colorectal Cancer

The grade describes how closely the cancer looks like normal tissue when seen under a microscope. This is sometimes used to distinguish whether a patient should get adjuvant treatment with chemotherapy after surgery.

• Grade 1 - Well differentiated
• Grade 2 - Moderately differentiated
• Grade 3 - Poorly differentiated
• Grade 4 - Undifferentiated

References

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