New approach to the substaging of node-positive colorectal adenocarcinoma

Background: Future developments in adjuvant modalities may require substagi ng of node-positive colorectal adenocarcinoma that is accurately indicative of individual prognoses, upon which therapeutic decisions (e.g., choice of agents and intensity of treatment) may be based. This study compares subst aging of node-positive colorectal cancer by venous invasion with substaging by three currently used methods, with respect to the ability of each metho d to define patient subsets that differ significantly in both disease-free and cancer-related survival rates. Methods: A total of 171 patients with node-positive colorectal cancer, who had undergone potentially curative resection at least 5 years earlier, were retrospectively substaged by the tumor, node, metastasis (TNM) N1/N2, Astl er-Coller C1/C2, Gastrointestinal Tumor Study Group (GITSG) C1/C2, and veno us invasion (positive/negative) methods. Disease-free and cancer-related su rvival curves were calculated (by the Kaplan-Meier method) and compared for statistical significance (using the log-rank test). Results: The separation of disease-free and cancer-related survival curves using the four methods of substaging node-positive colorectal cancer was as follows: TNM, P = .16 (not significant) and P = .12 (not significant); Ast ler-Coller, P < .01 and P = .006; GITSG, P = .067 (not significant) and P = .03; venous invasion, P = .016 and P = .007, respectively. Conclusions: Numerical substaging of node-positive colorectal cancer (TNM a nd GITSG methods) is an inferior predictor of prognosis, compared with subs taging by the T value (Astler-Coller) or venous invasion methods. We think that the latter method is the method of choice, because it separates patien ts who have only lymphatic metastasis from patients who display microscopic hematogenous spread as well. This separation obviously has biological/onco logical significance, and it may have practical therapeutic implications in the future.