Prognostic impact of the current Japanese nodal classification on outcomes in resected non-small cell lung cancer.

Abstract

The prognosis of N2 non-small cell lung cancer (NSCLC) has been reported to be heterogeneous. The recently revised Japanese nodal classification subcategorizes N2 disease according to the tumor-bearing lobe. We evaluated the prognostic impact of the Japanese nodal classification and its ability to define favorable N2 disease in resected NSCLC. A total of 496 patients with NSCLC who underwent lobectomy with systematic lymph node dissection between 1998 and 2009 were analyzed retrospectively. N2 status was subdivided into N2a-1 and N2a-2, according to the Japanese nodal classification. Overall survival (OS), disease-free survival (DFS), and clinicopathologic features were compared between the two groups. There were 67 cases with N2 disease. The outcome of resected N2a-2 NSCLC was far poorer than that of the N2a-1 group (5-year OS, 28% vs 62%, P < .001; 5-year DFS, 5% vs 35%, P < .001). Multivariate analysis revealed that pathologic N2a-2 was an independent prognostic factor (hazard ratio, 2.86; P < .05). Patients in the N2a-2 group showed more involved nodes and stations, less skip metastasis, and more locoregional recurrence than did patients in the N2a-1 group. The outcome of the N2a-1 group was satisfactory, and there was no significant difference in OS and DFS between N1 and N2a-1. The Japanese nodal classification is able to identify a favorable N2 subgroup in resected NSCLC. Nodal staging by the Japanese system should be considered when a clinical trial of N2 disease is designed.