Impact of total lymph node count on staging and survival after gastrectomy for gastric cancer: Data from a large US-population database

Background: Prognosis of potentially curable (M0), completely resected gastric cancer is primarily determined by pathologic T and N staging criteria. The optimal regional dissection extent during gastrectomy for gastric adenocarcinoma continues to be debated. Methods: A gastric cancer data set was created through structured queries to the Surveillance, Epidemiology, and End Results database (1973 to 1999). Relationships between the number of lymph nodes (LNs) examined and survival were analyzed for the stage subgroups T1/2N0, T1/2N1, T3N0, and T3N1. Results: In every stage subgroup, overall survival was highly dependent on the number of LNs examined. Multivariate prognostic variables in the T1/2N0M0 subgroup were number of LNs examined, age (for both, P < .0001), race (P = .0004), sex (P = .0006), and tumor size (P = .02). A linear trend for superior survival based on more LNs examined could be confirmed for all four stage subgroups. Baseline model-predicted 5-year survival with only one LN examined was 56% (T1/2N0), 35% (T1/2N1), 29% (T3N0), or 13% (T3N1). For every 10 extra LNs dissected, survival improved by 7.6% (T1/2N0), 5.7% (T1/2N1), 11% (T3N0), or 7% (T3N1). A cut-point analysis yielded the greatest survival difference at 10 LNs examined but continued to detect significantly superior survival differences for cut points at up to 40 LNs, always in favor of more LNs examined. Conclusion: Although the impact of stage migration versus improved regional disease control cannot be separated on basis of the available information, the data provide support in favor of extended lymphadenectomy during potentially curative gastrectomy for gastric cancer.