Mediastinal Up-Staging During Surgery in Non–Small-Cell Lung Cancer: Which Mediastinal Lymph Node Metastasis Patterns Better Predict The Outcome? A Multicenter Analysis

BackgroundUnexpected N2 involvement occurs in approximately 10% to 20% of patients with non–small-cell lung cancer (NSCLC) and patients’ prognostic factors remain unclear. The aim of this study was to evaluate prognostic factors in these patients.MethodsFrom January 2002 to December 2012, we retrospectively analyzed data of 550 patients with NSCLC with preoperative negative, but pathologic positive N2 involvement, who underwent anatomical lung resection and hilo-mediastinal lymphadenectomy, obtained from 6 institutions. An established prognostic factor panel and N2-type involvement were correlated to overall (OS), cancer-specific (CSS), and disease-free survival (DFS) using multivariate Cox Regression model. The following lymph node patterns were analyzed: number of resected nodes (#RNs), metastatic nodes (#MNs), ratio between #MNs and #RNs (NR), N2 subgroups proposed for the eighth TNM edition, and lobe-specific versus nonspecific metastasis.ResultsRegarding our cohort, 419 patients were staged IIIA (T1-2N2), 131 IIIB (T3-4 N2), 113 pT1, 306 pT2, 94 pT3, and 37 pT4; 5-year OS, DFS, and CSS were 34.1%, 20.1%, and 64.6%, respectively. Independent prognostic factor for OS, in the multivariable analysis, were as follows: NR <17% (P = .009), proposed N2 classification subgroups (P = .014), age <66 (P < .001), and pT (P = .005); for DFS: NR <17% (P = .003), adjuvant treatment (P = .026), and pT (P = .026); and for CSS: NR <17% (P = .008), grading (P = .001), and adjuvant treatment (P < .001).ConclusionOur study confirms that adjuvant therapy is fundamental and NR, in patients with unexpected N2 involvement, has a strong prognostic factor. In particular, a NR cutoff value of 17% could predict OS, DFS, and CSS in patients with NSCLC.