Background: Lymph node positivity is a strong prognostic indicator in many cancers including gastric cancer. The extent of surgical resection directly influences the number of lymph nodes available for staging, with the lesser D1 resection that is standard practice in non-Asian countries typically providing fewer nodes for analysis. The widely used AJCC TNM staging system has been criticized for under-staging and stage migration where fewer than 15 nodes are resected, which is often the case in these populations. The ratio of positive to total nodes harvested--Lymph Node Ration (LNR)--has been proposed as an improved and more widely applicable prognostic indicator.
Hypothesis: The LNR is a reliable and accurate prognostic indicator of survival in a Western gastric cancer population.
Methods: 9357 patients were acquired via a SEER case listing session with 2004-2011 gastric adenocarcinoma diagnoses. AJCC 7th edition nodal staging (N0: 0, N1:1-2, N2:3-6, N3:≥7 positive lymph nodes) and LNR positive nodal staging (PN0: 0%, PN1: 1-20%, PN2: 21-50%, PN3: 51-100% of examined nodes positive) were compared as respects seven year survivorship.
Results: Adjusted survival time ratios for AJCC nodal curves were less evenly distributed than were the percent positive nodal curves. Results of multiple regression reflected that survival time ratios of the percent positive nodal schema being more evenly spaced than those of the AJCC schema. Because BIC for AJCC, 41071.48, was larger than that for percent positive nodes, 41024.25, the LNR nodal system better explained survival than the AJCC nodal classification system.
Conclusion: LNR produced reliable and internally consistent survival curves for this population. LNR is an effective tool to predict survival in a western gastric cancer patient population, where the majority of the patients have limited lymph node dissection.
Keywords: Gastric cancer; Lymph node ratio; Survival.
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