Lymphatic Invasion Might Be Considered as an Upstaging Factor in N0 and N1 Gastric Cancer

(Background) The aim of this study was to investigate the prognostic impact of lymphatic invasion in gastric cancer, focusing on survival differences between N stage groups. (Methods) A total of 398 consecutive patients who underwent curative gastrectomy for primary gastric adenocarcinoma from January 2006 to December 2015 were analyzed retrospectively using data from a prospectively collected registry database. We compared various clinicopathological features and survival differences between lymphatic invasion-positive and -negative groups. (Results) Of the 398 patients, 141 (35.4%) showed lymphatic invasion. The lymphatic invasion-positive subgroup had poorer prognosis than the lymphatic invasion-negative subgroup in N0 (five-year survival rate: 87.8% vs. 73.6%, p = 0.048) and N1 (87.2% vs. 50%, p = 0.007) stage patients. The odds ratio (OR) of lymphatic invasion to five-year survival rate was 2.078 (95% confidence interval (CI), 1.103-3.916; p = 0.024). The presence of lymphatic invasion had worse effect on survival than age (OR, 1.807; 95% CI, 1.024-2.242; p = 0.029) or tumor depth (OR, 1.286; 95% CI, 1.078-1.897; p = 0.013) in N0 and N1 stage patients. The overall survival of patients with lymphatic invasion was not different from that of patients at a one-higher N stage without lymphatic invasion at any N stage. (Conclusions) The presence of lymphatic invasion may be the most important independent prognostic factor in N0 and N1 gastric cancer and might be an upstaging factor of N stage at any N stage. Therefore, in addition to the number of metastasized lymph nodes, the presence of lymphatic invasion should be included in N stage determination.