OA09.01 The Number or the Position is the Main Prognostic Factor for N2 NSCLC? A Validation of New IASLC N Staging Proposal

Abstract

The eighth edition of lung TNM does not change any N descriptors, but it suggests some potential changes that might be used in the next edition. In fact, N2 would be divided into three groups: pN2a1 (skip lymph-node involvement), pN2a2 (single mediastinal station with hilar involvement) and pN2b (multiple mediastinal involvement). The aim of this study was to verify the value of this classification proposal analyzing our recent surgical experience. We retrospectively selected all patients treated with lobectomy, bilobectomy or pneumonectomy for T1/T2 N2 NSCLC (VII TNM edition) in the period between 2006 and 2010. We excluded all patients who underwent any kind of extended resection and who had another active tumor at the time of operation. A systematic lymph-node dissection was always carried out according to the IASLC guidelines. All patients were then restaged according to the new IASLC proposal. Overall Survival (OS), Disease Free Interval (DFI) and most important variables were analyzed. Among 248 surgically treated pN2 patients, 108 entered our inclusion criteria. Pathology report showed a majority of T2 tumors (67,6%) and in almost half of cases an adenocarcinoma (50,9%); a mean number of 16,4 (DS 7,8) lymph-nodes were resected (5,8 (DS 2,9) from the hilum and 10,6 (DS 5,9) from the mediastinum). After restaging all cases with the new IASLC proposal we observed: 30 (27,8%) pN2a1; 57 (52,8%) pN2a2 and 21 (19,4%) pN2b. With a median follow up of 93 months, the median overall survival of the entire cohort was 27 months. pN2a1 had a significant better overall survival compared with the other two groups (p=0,020); conversely no statistically significant difference was found in OS between pN2a2 and pN2b. 1, 3 and 5-year survival for pN2a1, pN2a2 and pN2b were 90%, 81% and 71%; 53%, 37% and 24%; 45%, 26% and 19% respectively. Concurrently DFI was significantly better for pN2a1 (p=0,025). At univariate survival analysis age>65 years, more than 4 positive lymph nodes and postoperative complications were statistically significant variables. At the multivariate analysis only age and the number of positive lymph nodes were independent prognostic factors of a worse survival. Our experience partially validates the new proposal of IASLC of N2 staging. Patients with skip lymph-node metastasis (pN2a1) have a statistically significant better prognosis. Concurrently we observed and confirmed the important prognostic value of the number of the involved lymph-node, which should be considered as well in the next editions of the lung cancer staging system.