Background: Advanced, but potentially still curable gastric cancer (stages IIIA, IIIB, or stage IV M0) is associated with very high recurrence rates after gastrectomy. The value of an extended lymph node dissection (ELND) remains unclear in this setting. Methods: A resected gastric cancer data set was created through structured queries to the SEER 1973-2000 database. Relationships between the number of lymph nodes (LNs) examined and survival outcomes were analyzed for the stage subgroups characterized by the N categories N2 or N3, and transmural tumor extension (T categories T2b or T3). Results: The study group encompassed 1,377 patients, including T2b/3N2 (n = 1,076) and T2b/3N3 stage subgroups (n = 301). Total LN count (or number of negative LNs examined; P < 0.0001), number of positive LNs (P < 0.0001), age (P < 0.0001), primary site (P = 0.0002), T category (P = 0.0271), race (P = 0.0301) and gender (P = 0.0261) were independent prognostic survival predictors. A cut point analysis yielded the ability to detect significant survival differences for LN numbers up to 30 (N2) or up to 40 (N3), always in favor of the higher number of LNs examined. Best long-term survival outcomes were observed with negative LN counts of more than 15 (N2) or more than 20 (N3). Conclusions: Even in transmural or serosa-positive gastric cancer with advanced nodal involvement, more extensive LN dissection and analysis influences survival. Stage-based survival prediction depends on total LN number and number of negative LNs. The mechanism remains uncertain, but is not limited to stage migration. ELND during potentially curative gastrectomy is recommended even for advanced gastric cancer.
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