Inclusion Criteria:  Patients with resectable stage IIIA disease (according to American Joint Committee on Cancer [AJCC] lung cancer edition 7 or 8) who were included in the Tumor Thoracic Registry data base and in stage IIIA clinical trials which the sponsor is Fundación GECP. Patients with histologically N2 involvement confirmed Patients diagnosed as stage IIIA from 2010 and 2017 Patients who have received neoadjuvant platinum-based treatment and surgery Age ≥ 18 years at time of study entry PET /TC at diagnosis  Exclusion Criteria:  Patients who received chemoradiotherapy neoadjuvant treatment Patients who were not resected after neoadjuvant treatment Patients who were diagnosed after June 2017