Background The number of harvested (LNs) and metastatic nodes (LNs+) represents the most significant factor to define postoperative treatment and prognosis in colon cancer. However, its assessment may be inadequate causing an incorrect cancer staging. The lymph node ratio (LNR: the ratio between metastatic and resected nodes) has shown prognostic significance in many tumors; however, its role in colon cancer is not clearly elucidated. This study investigated LNR as a prognostic factor in node-positive colon cancers. Methods A total of 145 consecutive patients with nodepositive colon cancer who underwent curative surgery and adjuvant chemotherapy in a single oncologic unit entered this study. Results LNR ranged from 0.0416 to 0.9; it was clearly lower in pN1 than pN2 patients, and increased as tumor stage worsened. ROC analysis selected 0.1818 as the best LNR cutoff value. Low LNR patients did significantly better than high LNR patients; this difference was not dependent on the number of LNs and stronger than differences observed by grouping patients according to LNs or LNs+. When stratified by low and high LNR value, pN1 and pN2 patients, as well as stage III subgroups were shown to display substantially different outcomes. LNR was an independent prognostic factor for disease-specific survival, and the only covariate related to disease-free survival. Conclusions LNR was a robust prognostic indicator for node-positive colon cancers undergoing curative surgery. Because this ratio-based staging was demonstrated to reduce stage migration and to aid in identifying high-risk patients, it should be proposed as a standard tool for colon cancer staging.
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