Proposal of a new classification for stage III colorectal cancer based on the number and ratio of metastatic lymph nodes.

BACKGROUND

The objective of this retrospective study was to determine whether the current staging system for stage III colorectal cancer (CRC) is appropriate and to assess the value of the metastatic lymph node ratio (LNR) in predicting the prognosis of patients with stage III CRC.

METHODS

From 2000 to 2006 inclusively, 245 patients with stage III CRC underwent curative resection. The follow-up was closed in March 2012. Kaplan-Meier survival curves and log-rank tests were used for the survival analysis.

RESULTS

Survival time of patients with T3N1M0 was significantly better than that for patients in other subgroups of stage IIIB and similar to that of patients with stage IIIA disease. The greatest survival difference was found with 0.30 as the LNR cutoff point for patients with current stage III CRC. Survival time of patients with LNR ≤ 0.30 was significantly better than that of those with LNR > 0.30. rN1 included stage III patients with LNR ≤ 0.30, and rN2 included patients with LNR > 0.30. Survival time of patients with T4aN1(rN2)M0 staging was significantly worse than that for patients with T4aN1(rN1)M0 staging and similar to that of patients with stage IIIC CRC.

CONCLUSIONS

We propose an algorithm to incorporate LNR into the current American Joint Committee on Cancer staging system. In it the patients with T3N1M0 are excluded from the current stage IIIB and included in the stage IIIA group. Also, patients with T4aN1(rN2)M0 are excluded from the current stage IIIB group and included in the stage IIIC group.