Colon cancer 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 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. Adjunct staging of metastasis include Abdominal Ultrasound, MRI, CT, PET Scanning, and other imaging studies.
TNM staging system
The most common staging system is the TNM (for tumors/nodes/metastases) system, from the American Joint Committee on Cancer (AJCC). The TNM system assigns a number based on three categories. "T" denotes the degree of invasion of the intestinal wall, "N" the degree of lymphatic node involvement, and "M" the degree of metastasis. The broader 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. Details of this system are in the graph below:
|AJCC stage||TNM stage||2002 6th edition TNM stage criteria for colorectal cancer (superseded by 2010 7th edition)|
|Stage 0||Tis N0 M0||Tis: Tumor confined to mucosa; cancer-in-situ|
|Stage I||T1 N0 M0||T1: Tumor invades submucosa|
|Stage I||T2 N0 M0||T2: Tumor invades muscularis propria|
|Stage II-A||T3 N0 M0||T3: Tumor invades subserosa or beyond (without other organs involved)|
|Stage II-B||T4 N0 M0||T4: Tumor invades adjacent organs or perforates the visceral peritoneum|
|Stage III-A||T1-2 N1 M0||N1: Metastasis to 1 to 3 regional lymph nodes. T1 or T2.|
|Stage III-B||T3-4 N1 M0||N1: Metastasis to 1 to 3 regional lymph nodes. T3 or T4.|
|Stage III-C||any T, N2 M0||N2: Metastasis to 4 or more regional lymph nodes. Any T.|
|Stage IV||any T, any N, M1||M1: Distant metastases present. Any T, any N.|
In 1932 the British pathologist Cuthbert Dukes (1890-1977) devised a famous classification system for colorectal cancer. Several different forms of the Dukes classification were developed. However, this system has largely been replaced by the more detailed TNM staging system and is no longer recommended for use in clinical practice.
- Dukes' A: Invasion into but not through the bowel wall(90% 5-y survival)
- Dukes' B: Invasion through the bowel wall but not involving lymph nodes(70% 5-y survival)
- Dukes' C: Involvement of lymph nodes (30% 5-y survival)
- Dukes' D: Widespread metastases
An adaptation by the Americans Astler and Coller in 1954 further divided stages B and C
- Stage A: Limited to mucosa
- Stage B1: Extending into muscularis propria but not penetrating through it; nodes not involved
- Stage B2: Penetrating through muscularis propria; nodes not involved
- Stage C1: Extending into muscularis propria but not penetrating through it. Nodes involved
- Stage C2: Penetrating through muscularis propria. Nodes involved
- Stage D: Distant metastatic spread
- AJCC Cancer Staging Manual (Sixth ed.). Springer-Verlag New York, Inc. 2002.
- Who Named It, showing correct grammatical usage
- Kyriakos M: The President cancer, the Dukes classification, and confusion, Arch Pathol Lab Med 109:1063, 1985
- Dukes CE. The classification of cancer of the rectum. Journal of Pathological Bacteriology 1932;35:323
- AJCC (American Joint Committee on Cancer) Cancer Staging Manual, 7th ed, Edge, SB, Byrd, DR, Compton, CC, et al (Eds), Springer, New York 2010. p 143.
- Astler VB, Coller FA: The prognostic significance of direct extension of carcinoma of the colon and rectum. Ann Surg 139:846, 1954