Notable differences between available clinicopathological staging systems

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Clinical practice guidelines for the prevention, early detection and management of colorectal cancer > Notable differences between available clinicopathological staging systems

The two main clinicopathological staging systems currently used in Australia, the Australian clinicopathological staging (ACPS) system and pathological staging (pTNM — tumour, node, metastasis), may both be seen as extensions of the original Dukes staging method.

Apart from the symbols used to designate the stages, the two clinicopathological systems have some notable differences.

Serosal surface involvement

In the ACPS/Concord system, a “free” serosal surface is defined as a surface that is not adherent to another structure, and the involvement of such a surface by direct spread defines substage B2. A tumour that invades beyond the muscularis propria and into an adjacent structure may still be regarded as substage B1 if involvement of a free serosal surface is not demonstrated. In the pTNM system, a tumour that has infiltrated another structure is classified as T4b regardless of whether or not a free serosal surface is involved.

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Apical lymph node involvement

An apical lymph node is defined as a node within 1cm of the point of highest vascular pedicle ligation. Apical lymph node metastasis is associated with a worse prognosis than local lymph node metastasis, approaching that of distant metastasis.[1] The presence of an involved apical lymph node defines ACPS/Concord substage C2, but is not specified in the N classification of TNMA system that describes the amount and spread of cancer in a patient’s body. T describes the size of the tumour and its spread into nearby tissue; N describes the spread to nearby lymph nodes and M describes metastasis (spread of cancer to other parts of the body). staging.

Residual tumour

The ACPS/Concord stage D classifies the presence of residual tumour remaining after surgical resection of the primary tumour, at a line of resection (D1 - histological), and/or distant metastases (D2 - clinical or histological). pTNM stage IV applies only to cases with known distant metastases (clinical or histological). While the pTNM includes an optional R classification (table 8.4) for residual tumour, it is not used to assign a stage for such cases.

Data have been published supporting the inclusion of tumour in a line of resection in ACP stage D, and others have also documented the importance of this histological parameter[2]. Should the histological assessment of lines of resection be incorporated into pTNM staging and involvement [1] by tumour be a criterion for stage IV classification, then the two systems would be identical. In lieu of this, the use of the R code for residual tumour under the pTMM system would provide the necessary information to allow for closer correlation between the two staging systems (see Table 8.4). Notably the R classification definitions have changed in the latest edition of the AJCC staging manual. In the 7th edition R2 designated the total burden of residual disease, including the presence of distant residual tumour (e.g. unresected liver metastasis), whereas the 8th edition definition specifically refers only to locoregional residual tumour.[3][4]

Table 8.4. Residual Tumour R Classification

R — residual tumour
RX Presence of residual tumour cannot be assessed
R0 No residual tumour
R1 Microscopic residual tumour
R2 Macroscopic residual tumour at the primary cancer site or regional nodal sites (This designation is not used to indicate metastatic disease identified but not resected at surgical exploration)
Source: AJCC 2017[4]


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References

  1. 1.01.1 Newland RC, Dent OF, Lyttle MN, Chapuis PH, Bokey EL. Pathologic determinants of survival associated with colorectal cancer with lymph node metastases. A multivariate analysis of 579 patients. Cancer 1994 Apr 15;73(8):2076-82 Abstract available at http://www.ncbi.nlm.nih.gov/pubmed/8156513.
  2. Fielding LP, Arsenault PA, Chapuis PH, Dent O, Gathright B, Hardcastle JD, et al. Clinicopathological staging for colorectal cancer: an International Documentation System (IDS) and an International Comprehensive Anatomical Terminology (ICAT). J Gastroenterol Hepatol 1991 Jul;6(4):325-44 Abstract available at http://www.ncbi.nlm.nih.gov/pubmed/1912440.
  3. Edge SB, Compton CC. The American Joint Committee on Cancer: the 7th edition of the AJCC cancer staging manual and the future of TNM. Ann Surg Oncol 2010 Jun;17(6):1471-4 Abstract available at http://www.ncbi.nlm.nih.gov/pubmed/20180029.
  4. 4.04.1 Amin, M.B., Edge, S., Greene, F., Byrd, D.R., Brookland, R.K., Washington, M.K., Gershenwald, J.E., Compton, C.C., Hess, K.R., Sullivan, D.C., Jessup, J.M., Brierley, J.D., Gaspar, L.E., Schilsky, R.L., Balch, C.M., Winchester, D.P., Asare, E.A., Madera, M., Gress, D.M., Meyer, L.R. (Eds.). AJCC Cancer Staging Manual (8th edition). Springer International Publishing: American Joint Commission on Cancer; 2017 [cited 2016 Dec 28] Available from: http://www.springer.com/us/book/9783319406176#aboutBook.
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