Validation of a prognostic model including the number of harvested lymph-nodes in the setting of non-small cell lung cancer patients undergoing curative resection: a multicenter analysis

BACKGROUND: The prognostic role of the extension of lymphadenectomy in non-small-cell lung cancer is still a debated and intriguing issue. The aim of this study is to validate a prognostic score including the number of resected lymph-nodes previously reported using a large multicenter dataset. METHODS: From 01/2002 to 12/2012, data on 4858 NSCLC patients undergoing curative-intent surgery in six institutions were retrospectively reviewed. To test the discriminative ability of the model, composed of a panel of high-risk, pathologic stage, nodal status, age, number of Resected Nodes and intermediate risk factors (gender, grading, histology), was determined. The Kaplan-Meier method was used to estimate overall (OS), cancer-specific (CSS) and disease-free survival (DFS) curves, and the log rank test was adopted to evaluate the differences between groups. RESULTS: Pathological stages were: 1) Iin 46.5%, IIin 24.1%, IIIin 27.8% and IVin 1.6% of cases. Overall, 5-year OS, CSS and DFS were 54.6%, 76.7% and 44.8%, respectively. Stratifying the sample of 3948 patients with complete data into low-risk (LR, #107), Intermediate-risk (IR, #1268) and High-Risk (HR, #2573) groups, the optimal prognostic discrimination power of this score was confirmed (C-statistics: 0.71, 95%CI 69-73). Specifically in LR, IR and HR, 5-year OS was 83.5%, 66.4% and 46.2% (P<0.0001), 5y-CSS was 95.8%, 89% and 69% (P<0.0001), and 5y-DFS was 74.7%, 59.1% and 35.5% (P<0.0001), respectively. CONCLUSIONS: Our study confirms the optimal prognostic discrimination power of the previous prognostic model including the number of harvested nodes.