New assessment of the N1-N2 substaging in stage III colorectal cancer

Purpose: The five-year survival rates of patients with stage III colorectal cancer have been reported widely ranging from 22 to 69 percent. Hence, reliable substaging is important for the management of stage III colorectal cancer patients. Therefore, we tried to assess the substages and investigate the possibility of other discriminating numbers for nodal substaging. Methods: The 381 patients with node-positive colorectal cancer who had undergone surgery, were retrospectively categorized by the number of positive nodes. The patients were grouped in five ways, and each grouping was divided into two subgroups according to the number of positive nodes. The subgroups of each grouping were as follows; in LN1 group, N1=1, N2>1; in LN2 group, N1=2, N2>2; in LN3 group, N1=3, N2>3; in LN4 group, N1=4, N2>4; in LN5 group, N1=5, N2>5. We compared the survival rate of each groups. Results: Node-positive patients had a five-year survival rate of 55.2 percent. The statistical differences between the N1 and N2 subgroups of each grouping were as follows: LN1 group (P=0.0128), LN2 group (P=0.0052), LN3 group (P=0.6268), LN4 group (P=0.1480), and LN5 group (P=0.6875). Conclusion: There were significant differences in the five-year survival rates between N1 and N2 in the LN1 group and LN2 group, but there were no differences between N1 and N2 in the other groupings. These data raise the possibility that a novel N1~N2 substaging (N1: 1∼2; N2: >2) is superior to the current N1∼N2 substaging (N1: 1∼3; N2: >3).