The prognostic role of metastatic lymph node ratio in colon cancer: a retrospective cohort study on 241 patients in a single center

BACKGROUND: The detection of nodal status is based on examination of lymph nodes (LN) after the tumor surgical resection and the current guidelines recommend examining at least 12 regional LN. An inadequate number of examined LN may lead to a lower N stage or to a false-negative nodal disease. To overcome these issues, many authors proposed to consider the metastatic lymph node ratio (mLNR). MLNR is the ratio of the number of metastatic LN to the number of examined LN. METHODS: Two hundred forty-one colon cancer (CC) specimens from patients who had undergone surgical resection between January 2010 and December 2015 at the General Surgery Unit of Parma University Hospital were analyzed. mLNR, which is defined as the ratio of the number of positive LN to the number of examined LN, was calculated in CCs with LN metastasis. In this study we focused on the following mLRN cutoffs: <0.15, 0.15-0.3 and >3 and we evaluated the prognostic implication of mLNRs. RESULTS: Regarding the impact of examined LN on involved LN in CC, our results showed that the number of involved LN increased with the increasing number of examined LN (P=0.03). We found a significant correlation between OS and RFS rate of patients with CCs and mLNR. Patients with mLNR<0.15 were associated with better OS and RFS rate whereas patients with mLNR>0.3 were associated with worse OS and RFS rate. OS rate for patients with a mLNR<0.15 was 95.24% (89-100%) at 1 year, 83.27% (72.7-95.4%) at 3 years and 68.07% (55.1-84.1%) at 5 years whereas patients with a mLNR>0.3 had an OS rate of 51.7% (34.6-77.3%) at 1 year, 36.55% (20.08-64.3%) at 3 years and 31.33% (16.5-59.4%) at 5 years. RFS rate for patients with a mLNR<0.15 was 100% (100-100%) at 1 year, 92.2% (84-100%) at 3 years and 85.2% (73.8-98.31%) at 5 years whereas patients with a mLNR>0.3 had a RFS of 63.2% (42.8-93.58%) at 1 year and 54.2% (33.1-88.93%) at 3 and 5 years. CONCLUSIONS: The prognostic value of pN stage could be more accurate if we consider both the number of LN metastasis and harvested LN. This can be achieved by using the mLNR that can be a useful tool in daily practice to predict the prognosis of patients who undergone surgery for CC.