CORRESPONDENCE

Re: Colon Cancer Survival Rates With the New American Joint Committee on Cancer Sixth Edition Staging

Stephen B. Edge, Leslie H. Sobin, David L. Page, Mary K. Gospodarowicz, Frederick L. Greene, David P. Winchester

Affiliations of authors: American Joint Committee on Cancer, Chicago, IL (SBE, DLP, FLG, DPW); International Union Against Cancer, Geneva, Switzerland (LHS, MKG)

Correspondence to: Stephen B. Edge, MD, American Joint Committee on Cancer, 633 North Saint Clair Street, Chicago, IL 60603 (e-mail: stephen.edge{at}rosewellpark.org).

O'Connell et al. (1) showed that the stage groupings in the newer sixth edition of the tumor-lymph node-metastasis (TNM) staging system more distinctly stratify survival than the fifth edition (2,3). However, survival was worse with T4N0M0 (stage IIB) than with T1-2N1M0 (stage IIIA) disease. Review of 351 000 colon cancer case records in the National Cancer Data Base confirms this finding (A. Stewart, personal communication). In the accompanying editorial, Burke (4) states that this breaks a fundamental rule of the TNM staging system—that survival should decrease with increasing stage grouping. On this basis, he recommends the American Joint Committee on Cancer (AJCC) revert to the fifth edition of TNM staging for colon cancer staging.

In most cases, survival usually decreases with each higher stage group. However, stage group primarily reflects increasing anatomic extent of disease. For colon cancer, stage II is local disease with negative lymph nodes and stage III denotes positive lymph nodes. The recognition that T4N0 tumors had a worse prognosis than T3N0 was the basis for dividing stage II of the fifth edition into stages IIA and IIB in the sixth edition. The findings of O'Connell et al. support this division and do not require that we abandon this improved disease classification.

Burke also raises more fundamental questions regarding TNM: that it fails to account for the prognostic impact of response to presurgical therapy and does not allow for use of nonanatomic biologic factors. Further, he states that the TNM system that assigns cases to stage groups, or "bins," should be replaced by programs that quantify prognosis for an individual.

Grouping patients with similar disease is necessary for assessing the impact of treatments in similar patients and for population surveillance of cancer incidence and outcome. However, this procedure does not preclude the use of any factors that affect cancer prognosis or the future reorganization of groups around such factors. It is everyone's hope that advancing science will fundamentally change understanding of cancer prognosis. The challenge is to identify those factors that are sufficiently robust that they can be reliably measured and applied to all cases.

Toward this goal, the AJCC examined nonanatomic factors and alternate staging schemas for the sixth edition revisions of the TNM staging system. International workshops addressed the use of neural networks and nonanatomic prognostic factors, with concrete recommendations used in revising TNM staging (5). The International Union Against Cancer (UICC) also published a monograph, now in its second edition, that discusses both the methodology for assessing prognostic factors and specific factors at each anatomic site of cancer and includes a chapter on the use of neural networks (6,7).

Another advance to allow the use of new prognostic factors, developed by the AJCC in collaboration with the other cancer surveillance organizations, is the Collaborative Staging System, a standardized data collection platform for cancer staging being implemented across North America by all hospital and population registries (http://www.cancerstaging.org). A key component is that it includes fields for collection of disease—specific non-anatomic factors that may affect prognosis.

Staging with presurgical therapy is based on physical examination and imaging studies. For population surveillance and examination of overall benefits from therapy, the extent of cancer at the time of diagnosis is the critical issue. However, response to treatment may provide useful prognostic information. Similarly, comorbidity affects outcome. Future prognostic algorithms and cancer data systems will certainly include such information.

The AJCC and UICC disagree that the TNM staging system should revert to the fifth edition staging system for colon cancer. We agree that the TNM staging system should undergo continuous scrutiny and periodic revision to give patients and doctors the best possible information and to provide a basis for study of the societal impact of improvements in cancer prevention, diagnosis, and treatment.

REFERENCES

(1) O'Connell JB, Maggard MA, Ko CY. Colon cancer survival rates with the new American Joint Committee on Cancer sixth edition staging. J Natl Cancer Inst 2004;96:1420–5.[Abstract/Free Full Text]

(2) Greene FL, Page DL, Fleming ID, et al. (editors). AJCC cancer staging manual. 6th ed. New York (NY): Springer-Verlag; 2002.

(3) Sobin LH, Wittekind CH (editors). UICC TNM classification of malignant tumors. 6th ed. New York (NY): Wiley; 2002.

(4) Burke HB. Outcome prediction and the future of the TNM staging system. J Natl Cancer Inst 2004;96:1408–9.[Free Full Text]

(5) Yarbro JW, Page DL, Fielding LP, Partridge EE, Murphy GP. American Joint Committee on Cancer prognostic factors consensus conference. Cancer 1999;86:2436–46.[CrossRef][ISI][Medline]

(6) Gospodarowicz MK, Henson DE, Hutter RVP, O'Sullivan B, Sobin LH (editors). Prognostic factors in cancer. 2nd ed. New York (NY): Wiley; 2001.

(7) Rodvald DM, McLeod DG, Brandt JM, Snow PB, Murphy GP. Artificial neural networks for physicians: a technology introduction. In: Gospodarowicz MK, Henson DE, Hutter RVP, O'Sullivan B, Sobin LH (editors). Prognostic factors in cancer. 2nd ed. New York (NY): Wiley; 2001.


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