Department of Pathology, SGPGIMS, Lucknow, India.

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Staging of Colo-rectal Cancers 

The clinicians and pathologists use a number of characteristics to describe properties of tumors, including site, size, extent, histological type and histological grade, etc. The importance of such characteristics or variables lies in their ability to discriminate between subsets of tumors that may have a different outcome. Some variables have a greater ability for such discrimination. In general, for a majority of tumors including colorectal cancers, the stage of the tumor is the single most important such variable. The staging of a tumor uses a convention of a shorthand notation to provide a summary of extent of the primary tumor, which can assist the clinicians in planning of treatment and gives an indication of prognosis. Accurate and consistent use of a staging system would also help in evaluation of results of treatment, comparative studies between different centers and on-going investigations of tumor therapy and behavior. 

The staging of colorectal cancers is complicated by the fact that multiple staging systems are in use and there is no agreement on which staging system should be used. Although most staging systems rely on the depth of tumor invasion and absence or presence of nodal and distant metastases, there is no consensus on how various categories should be grouped. Since the description of the first practical staging system by Dukes,¹ the evolution and modification of staging systems over last 60 years with newer systems using similar notations to represent different stages has resulted in considerable confusion and misinterpretation. Apart from the Dukes’ system¹ which is still widely used, the other popular systems include the classification described by Astler and Coller,² and the tumor-node-metastasis (TNM) classification of the Union Internationale Contra le Cancer (UICC) and the American Joint Committee on Cancer (AJCC).³

The Dukes’ Staging System

The original Dukes’ system¹ was described for rectal carcinomas that can also be applied to carcinomas of the colon. Stage A tumors were defined as those limited to the wall (not extending beyond muscularis propria), stage B as those extending through the wall (into subserosa and/or serosa, or extra-rectal tissues), and stage C as those having lymph node metastasis. The stage C was later subdivided by Dukes himself into C1 when only perirectal nodes were positive and C2 when nodes at the point of mesenteric blood vessel ligature (called apical nodes) were involved (Fig. 1).⁴

The stage D was added still later and was characterized by presence of tumor beyond the limits of surgical resection.⁵

Fig. 1. The Dukes’ Staging System (see text for details).

The Astler-Coller Staging System

This system was proposed in 1954 and has resulted in some confusion because it is often misinterpreted as related to the Dukes’ system. The original scheme² had five stages, A was limited to the mucosa, B1 involved muscularis propria but did not penetrate it, B2 penetrated the muscularis propria, and C1 and C2 were counterparts of B1 and B2 with nodal metastases (Fig. 2). Since then, later modifications have added three more stages. B3 represents involvement of adjacent structures, C3 is B3 with nodal metastasis, and D signifies presence of distant metastasis.⁶

Fig. 2. The Astler-Coller Staging System (see text for details).

The TNM Staging System

The systems described by AJCC and UICC using TNM classification were unified into one in 1988.^7,8 The latest revision (1997) has introduced some minor modifications.³ The TNM system compartmentalizes carcinomas according to the depth of invasion of the primary tumor, the absence or presence of regional lymph node metastases, and the absence or presence of distant metastases (Table I, Fig. 3). The possible number of resulting categories is too large (24 or more if Tis is included) for practical usage. Various categories are therefore grouped under stages I through IV (Table II). Of the other two main classifications, cTNM is based on evidence acquired before treatment and pTNM is based on clinical staging and information obtained at surgery and pathological examination of the resected specimen. 

Many additional descriptors are used in conjunction with the TNM classification. The R classification refers to presence of residual carcinoma after treatment. The G classification reflects inclusion of histological grading. The C factor is based on certainty of diagnosis, L represents lymph vessel invasion, and V reflects venous invasion. It is important to remember that a minimum of twelve lymphnodes should be examined for proper assessment of the N cateogory. A tumor nodule measuring three cms or more in diameter in the perirectal or pericolic adipose tissue even without histological evidence of residual lymphnode tissue in the nodule is classified as regional nodal metastasis. 

Table I. The TNM Staging Classification for Colorectal Carcinomas (1997).

 
Table II. The Group Staging criteria for TNM Classification (1997).

 

Fig. 3. The TNM Staging System (see text for details).

The metastatic deposits in nodes distant from those surrounding the main tumor or its main artery in the specimen (e.g. external iliac or para-aortic nodes) are counted as distant metastases and would represent M1. The specified regional lymphnodes for the colorectal cancers for different anatomical sites are given in table III.⁹

Table III. Lymph Nodes designated as regional for Colorectal Carcinomas 

Other Staging Systems

Many other staging systems have been proposed trying to define a scheme which is more predictive. The Gunderson-Sosin modification of the Astler-Coller system subclassifies B2 and C2 tumors into those with microscopic (B2m or C2m) and gross (B2m+g or C2m+g) invasion of tumor through the bowel wall.¹⁰ The Gastrointestinal Tumor Study Group (GITSG) classification uses the number of nodes (1-4 and >4) involved to separate stages C1 and C2, respectively.¹¹ The classification by Jass et al uses absence or presence of transmural penetration, pushing or infiltrative margin of primary tumor, absence or presence of conspicuous peritumoral lymphocytic infiltrate, and number of positive nodes for a mathematical stratification.¹² Many other local and institutional schemes exist reflecting the current controversies. 

Which staging system to use?

The question is still unresolved although many authorities recommend the use of the TNM classification for reporting results. It is, however, relatively complex as compared to the other systems. The major contribution of the Astler-Coller system was stress on the prognostic importance of the level of direct spread in stage C tumors. As it has proved to be an independent factor in determining prognosis, the Astler-Coller system has remained popular. However, it does not take into account the number of positive nodes, another important independent prognostic factor. Although the Dukes’ system has attracted criticism because of imprecise definitions, it remains appealing because of its simplicity and some studies recommend it as the most consistent algorithm related to the prognosis.¹³ The only modification it might require is the subdivision of category C according to Astler-Coller and/or TNM systems. The involvement of margins is not properly addressed in any of the widely used staging systems. The failure to account for the presence of residual tumor is a major limitation of all purely pathologic staging systems. Ultimately, the choice of a staging system remains institutional. However, it should be ensured that the staging system in use is well understood by all concerned, is consistently and accurately used, and can be translated into the other popular systems, as far as possible. 

References

Dukes CE. The classification of cancer of the rectum. J Pathol 1932;35:323.

Astler VB, Coller FA. The prognostic significance of direct extension of carcinoma of the colon and rectum. Ann Surg 1954;139:846.

Colon and rectum. In: American Joint Committee on Cancer: AJCC Cancer Staging Manual. Philadelphia: Lippincott-Raven Publishers, 5^th ed, 1997:83.

Gabriel VB, Dukes C, Bussey HJR. Lymphatic spread in cancer of the rectum. Br J Surg 1935;23:395.

Dukes CE. The surgical pathology of rectal cancer. J Clin Pathol 1949;2:95.

Rosch T. The new TNM classification in gastroenterology. Endoscopy 1998;30:649.

International Union Against Cancer. TNM classification of malignant tumours. ed. 4. Berlin: Springer-Verlag, 1987.

American Joint Committee on Cancer. Colon and rectum. In: Beahrs OH, Henson DE, Hutter RV, Myers MH, eds. Manual for staging of cancer. ed 3. Philadelphia: JB Lippincott, 1988:75.

Compton CC, Henson DE, Hutter RVP, Sobin LH, Bowman HE, for Members of the Cancer Committee, College of American Pathologists. Updated protocol for the examination of specimens removed from patients with colorectal carcinoma: A basis for checklists. Arch Pathol Lab med 1997;121:1247.

Gunderson LL, Sosin H. Areas of failure found at re-operation (second or symptomatic look) following "curative surgery" for adenocarcinoma of the rectum: clinicopathologic correlation and implications for adjuvant therapy. Cancer 1974;34:1278.

Gastrointestinal Tumor Study Group. Prolongation of the disease-free interval in surgically treated rectal carcinoma. N Engl J Med 1985;312:1465.

Jass JR, Love SB, Northover JM. A new prognostic classification of rectal cancer. Lancet 1987;1:1303.

Fisher ER, Sass R, Palekar A, Fisher B, Wolmark N, contributing National Surgical Adjuvant Breast and Bowel Projects Investigators. Dukes’ classification revisited: Findings from the National Surgical Adjuvant Breast and Bowel Projects (Protocol R-01). Cancer 1989;64:2354.

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