Distribution of lymph node metastasis is a prognostic index in patients with stage III colon cancer.

Background: In the TNM classification of colorectal carcinoma, N-staging is dependent on the number of metastases; in the Japanese classification system, staging usually has been based on the distribution of metastases (N1, paracolic; N2, along the major vessels; N3, at the root of major vessels). The aim of our study was to examine whether the concept of the distribution of nodal metastasis could improve the TNM classification for colorectal cancer.

Methods: We studied the survival rates of 485 and 136 patients with stage III colonic and rectal cancer, respectively, who underwent curative surgery between 1979 and 1998. The patients were categorized into 4 groups: group 1, TNM-N1 classified in J-N1; group 2, TNM-N2 in J-N1; group 3, TNM-N1 in J-N2-3; and group 4, TNM-N2 in J-N2-3.

Results: In the colon cancer arm, the 5-year survival rates of the patients in groups 1 to 4 were 74%, 51%, 52%, and 54%, respectively. There was a significant difference in survival rate between groups 1 and 3 (P = .0002). Thus, in colon cancer, nodal metastasis along the major vessels was a bad prognostic factor, even though the number of nodes that were involved was <4. In the rectum cancer arm, the 5-year survival rates of the patients in each group were 65%, 39%, 60%, and 32%, respectively. Only the number of nodal metastases was an independently significant prognostic variable.

Conclusion: This study suggests that adding the concept of nodal distribution to the conventional TNM staging of colon cancer will improve the accuracy in the evaluation of the nodal status.