Colorectal Cancer Staging: Reappraisal of N/PN Classification

Abstract

PURPOSE: Current American Joint Committee on Cancer and the Union Internationale Contre le Cancer TNM classification disregards location of positive nodes, discontinuing N3 category, which constitutes a major modification to 1987 version. This study was designed to assess the impact of the recategorization of former N3 cases and the reliability of the current N1-N2 subcategorization of Stage III patients. METHODS: Prospectively collected data from 1,391 patients (55.8 percent males; median age, 64 (range, 21-97) years), operated on with curative intent between 1980 and 1999, were analyzed. The median follow-up was 60 (interquartile range, 27-97) months with 129 cases lost to follow-up. RESULTS: Of positive node cases, 25.3 percent were former N3. Among them, 30.5 percent migrated to the N1 group and 69.5 percent to the N2 group. The proportions of former N3 cases in N1 and N2 groups were 12.5 percent and 46.1 percent, respectively (P<0.001). Node-positive patients had an actuarial five-year survival rate of 56.7 percent (95 percent confidence interval, 53-59), with a significant difference between N1/N2 categories (63.6 vs. 44.1 percent, respectively; P<0.001). Although apical node involvement and more than three positive nodes were associated with poorer outcomes in univariate analysis, only the number of positive nodes had independent association (hazard ratio, 1.6 (range, 1.2-2.2); P<0.001). Integration of former N3 cases did not modify outcomes. CONCLUSIONS: The recategorization of former N3 involved a high proportion of positive node cases. Current N1/N2 categories clearly defined different outcomes and were not modified by the integration of former N3.