Validation of a new classification system for curatively resected colorectal adenocarcinoma.

Background: The parameters within which colorectal adenocarcinoma is currently staged are often insufficient for decisions regarding therapy after potentially curative surgery. Consequently, oncologists make frequent use of additional prognostic indicators when assessing individual prognosis and selecting patients for adjuvant systemic treatment. Follow-up programs are generally uniform for all patients, regardless of disease stage and prognosis. As a result, patients with a favorable prognosis are needlessly subjected to stressful, costly follow-up too early and too frequently. This study was conducted to validate a new classification system that is a superior predictor of individual prognosis following curative surgery and may serve as a guide for personalized, cost-effective postoperative management and follow-up.

Methods: A total of 231 American colorectal carcinoma patients who underwent curative resection were retrospectively staged according to a new classification (containing 4 stage-groups) for curatively resected colorectal adenocarcinoma. This classification is based on statistical analysis of the impact on prognosis of numerous characteristics of 363 consecutive Israeli colorectal carcinoma patients who underwent curative resection. All the patients in both cohorts had had surgery at least 5 years previously. The new classification is based on three histologic variables (venous invasion, depth of primary tumor penetration, and regional lymph node status) and a scoring system that correlates higher numeric score with worse prognosis. In both cohorts, the new classification was compared with the Dukes, Astler-Coller, and TNM staging systems for patient distribution and survival (both disease free and cancer-related survival).

Results: In both cohorts, the 4 stage-groups of the new classification differed significantly in both the rate of and the time to first recurrence and cancer-related death, with progression from Group 4 to Group 1. Groups of high risk lymph node negative patients were defined, and lymph node positive patients were subdivided according to prognosis. It is suggested that, by using this new classification as a guide, selection for adjuvant systemic treatment may be refined, and postoperative follow-up may be personalized and therefore more cost-effective.

Conclusions: The new classification for curatively resected colorectal adenocarcinoma, based on an analysis of the Israeli cohort and validated in the American cohort, is superior to the Dukes, Astler-Coller, and TNM staging systems as a predictor of individual prognosis, most probably because it incorporates the microscopic forerunner of distant, hematogenous spread (i.e., venous invasion) with the locoregional parameters of extent of disease (i.e., T and N values). It is suggested that the new classification may serve as a guide for more refined selection of patients for adjuvant systemic treatment and for individualized and more cost-effective postoperative follow-up. The new classification is simple and easy to use, requires no sophisticated equipment or tests, and can be applied in any health care system worldwide.