The prognostic effect of metastatic lymp nodes ratio staging in stage III colorectal cancer

초록

Purpose) Recent studies have focused on lymph node ratio (LNR), defined as the ratio of the number of tumor infiltrated nodes to the total retrieved lymph node numbers, as a noteworthy prognostic factor in colorectal cancer. However, the standard of optimal LNR is still not entirely investigated for LNR staging, defined as categorization based on cutoff point of LNR. So, the purpose of this study is to determine the cutoff point of optimal LNR and to identify the prognostic value of LNR staging based on this point Method) A retrospective analysis was made of patients who were taken to surgery for colon or rectal cancer at Inha University hospital between January 2001 and September 2014. Total of 412 patients, comprising 248 with colon cancer and 164 with rectal cancer, who had lymph node metastasis on final pathologic results (stage III) were included in this study. A cutoff point was obtained using the minimum p-value approach by log rank test with a Bonferroni adjustment for multiple comparisons, which detected an optimal cutoff point showing the lowest p-value by log rank test for 5-year cancer free survival (CFS) according to LNR in all patients. Based on the optimal cutoff value, the patients in respective cancer were divided into two groups. For estimating the effect of LNR staging on CFS according to current nodal staging (N1 and N2), the patients in respective N group were divided in the same way. CFS by LNR staging was analyzed using Kaplan-Meier method and log-rank test. Cox proportional hazards model was performed to estimate hazard ratios (HR) and 95% confidence interval (CI) for CFS comparing LNR staging. Results) The optimal cutoff values for CFS according to LNR were 0.66 and 038 for colon cancer and rectal cancer, respectively. In a multiple Cox proportional hazards model, LNR staging showed a significant prognostic effect on CFS in both colon and rectal cancer. The HR (95%CI) for CFS was high