New metastatic lymph node ratio system reduces stage migration in patients undergoing D1 lymphadenectomy for gastric adenocarcinoma.

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 >or=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 >or=15 nodes examined; Nr1: 0 <or= N ratio <or= 0.3; Nr2: 0.3 < N ratio <or= 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 >or=15 nodes examined. When we stratified by N ratio intervals, there was no significant difference in overall survival in patients with <15 versus >or= 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.