P-349 Clinical significance of lymph node radio to predict prognosis in colon cancer

Abstract

Metastases to regional lymph nodes (LN) has been considered to be a strong outcome predictor following surgical resection and a key determinant factor for adjuvant chemotherapy in colon cancer. According to the tumor-node-metastasis system reflected by the American Joint Committee on Cancer (AJCC), which has been the most popular cancer staging system, patients with positive LN involvement without distant metastasis are classified as stage III and they are subclassified into pN1 and pN2 based on the number of involved LN. However, in the current staging system, low LN harvest may lead to inadequate nodal staging which might result in overestimation of patient prognosis. In this perspective, recent studies recommended the lymph node ratio (LNR; the number of positive LN divided ty the number of harvested LN) as a prognostic indicator, rather than current nodal staging by AJCC. In the present study, we investigated the clinical significance of LNR to predict survival outcomes in colon cancer. Patients who underwent radical resection for colon cancer and presented with positive LN involvement from January 2014 to December 2016 were included in the present study. Among the included patients, who were candidates for adjuvant chemotherapy, patients who had not undergone chemotherapy were excluded. Patient medical records were reviewed retrospectively and the number of harvested LN, positive LN and other pathological factors for prognosis including pT stage by AJCC, lymphovascular invasion, perineural invasion and histologic grade were recorded. As survival outcomes, disease-free survival (DFS) and overall survival (OS) were investigated. A total of 84 patients with positive LN involvement who underwent adjuvant chemotherapy were enrolled in the present study. Their median duration of follow-up was 43.5 months (interquartile range, 29.8-56.8 month). The median number of harvested LN was 22 (interquartile range, 16-27) and positive LN was 2 (interquartile range, 1-5). Median LNR was 14.3% (interquartile range, 5.3-25.0%). Hazard ratio (HR) for DFS of LNR by multivariate Cox regression analysis including putative confounding factors for prognosis was 1.009 (95% confidence interval [CI], 0.991-1.027), which was not statistically significant. (p=0.338). For OS, the HR of LNR was 1.005 (CI, 0.667-1.005) and it was not significant either. In the present study, LNR was not a significant predictor for prognosis in colon cancer. Further evaluation with a larger cohort with detailed co-variate investigation would be required to verify the clinical significance of LNR.