New Metastatic Lymph Node Ratio System Reduces Stage Migration in Patients Undergoing D1 Lymphadenectomy for Gastric Adenocarcinoma

Abstract

Background: The American Joint Committee on Cancer (AJCC)/International Union Against Cancer (UICC) staging system for gastric cancer incorporates the absolute number of metastatic lymph nodes (N status) and is optimally used when ≥15 nodes are examined. The ratio of metastatic to examined nodes (N ratio) is an effective prognostic tool, but has not been examined in Western patients undergoing primarily D1 lymphadenectomy. Methods: Two hundred and fifty seven patients with gastric adenocarcinoma who underwent gastric resection between 1995 and 2005 at our institution were examined. Novel N ratio intervals were determined using the best cutoff approach (Nr0: N ratio = 0 and ≥15 nodes examined; Nr1: 0 ≤ N ratio ≤ 0.3; Nr2: 0.3 < N ratio ≤ 0.7; and Nr3: N ratio > 0.7). Overall survival was examined according to N status and N ratio. Results: 83% of patients underwent D1 lymphadenectomy with a median of 14 lymph nodes examined. Overall survival stratified by N status was significantly different in patients with <15 nodes examined compared with those with ≥15 nodes examined. When we stratified by N ratio intervals, there was no significant difference in overall survival in patients with <15 versus ≥ 15 nodes examined. On multivariate analysis, N ratio but not N status was retained as an independent prognostic factor. Conclusions: The use of N status for staging patients undergoing primarily D1 lymphadenectomy results in significant stage migration due to varying numbers of nodes examined. Use of N ratio reduces stage migration and may be a more reliable method of staging these patients.