Background: Future developments in adjuvant modalities may require substaging 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 substaging of node-positive colorectal cancer by venous invasion with substaging by three currently used methods, with respect to the ability of each method 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, Astler-Coller C1/C2, Gastrointestinal Tumor Study Group (GITSG) C1/C2, and venous invasion (positive/negative) methods. Disease-free and cancer-related survival 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); Astler-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 and GITSG methods) is an inferior predictor of prognosis, compared with substaging by the T value (Astler-Coller) or venous invasion methods. We think that the latter method is the method of choice, because it separates patients who have only lymphatic metastasis from patients who display microscopic hematogenous spread as well. This separation obviously has biological/oncological significance, and it may have practical therapeutic implications in the future.