Survival impact of node zone classification in resected pathological N2 non-small cell lung cancer

We assessed the prognostic value of the 'Zone-classification' which has been proposed by the Japanese Association for Lung Cancer (JALC) for mediastinal nodal metastases in non-small cell lung cancer (NSCLC). Among 357 NSCLC patients who underwent curative surgery, 46 patients with pathological (p) N2 disease were divided into two groups as follows: 32 patients in whom the nearer zone was involved were classified as the pN2a-1 group, and 14 patients in whom the further mediastinal node station was involved were classified as the pN2a-2 group. The proportions of patients with non-adenocarcinoma histology, with multiple station metastases with the involvement of four or more nodes, and who underwent pneumonectomy, were higher in the pN2a-2 group. The 'Zone-classification' proved to be a significant prognostic factor in a univariate analysis (the 5-year overall survival rate, 7.1% for pN2a-2 versus 21.9% for pN2a-1; P < 0.01). A multivariate analysis confirmed that pN2a-2 sub-classification (hazard ratio 2.77; P = 0.03) and undergoing pneumonectomy (hazard ratio 4.86; P < 0.01) were independent and significant factors in predicting a poor prognosis. In pN2 NSCLC patients, the involved mediastinal zone according to the primary tumour site was important in prediction of survival.