N2 lung cancer is not all the same: an analysis of different prognostic groups

OBJECTIVES: The International Association for the Study of Lung Cancer (IASLC) recently proposed a change in the staging system for N2, based on the metastatic station number: N2a1 (a single metastatic station with no hilar involvement), N2a2 (a single metastatic station with hilar involvement) and N2b (multiple metastatic stations). The aim of our study was to validate the IASLC proposal in a cohort of patients with pathological N2 disease. METHODS: All patients with pathological T1-T2 N2 non-small-cell lung cancer who were operated on between 2006 and 2010 in our department were enrolled. The patients had lobectomy, bilobectomy or pneumonectomy without induction therapy; patients with any type of extended resection were excluded. All patients had adjuvant treatment. The impact of the new IASLC proposal on the overall and disease-free survival rates was then analysed. RESULTS: Ninety-three patients were selected. The median follow-up period and overall survival time were 92 and 28.8 months, respectively. According to the new IASLC proposal, we observed 22 cases of N2a1, 54 N2a2 and 17 N2b. Patients with N2a1 had a significantly better overall survival than those with N2a2 and N2b (P = 0.041); the difference between N2a2 and N2b was not significant (P = 0.19). Patients with N2a1 squamous cell carcinoma had a significantly better overall survival than those with other histological diagnoses (P = 0.046). The disease-free interval was longer in patients with N2a1 than those in other groups (P = 0.021). CONCLUSIONS: Our experience partially validates the IASLC proposal; the introduction of quantitative criteria for N staging might improve stratification of patients and the assignment to the correct therapeutic path.