Inclusion Criteria:  Eligible patients should be ones who have stage I-IIIA non-small cell lung cancer (NSCLC) and undergo surgical resection with or without neoadjuvant chemotherapy as part of standard treatment, and have a information of demographics, smoking history, preoperative clinical data, and follow -up data including adjuvant therapy, relapse, and treatment at relapse.  We will include the three major NSCLC histologic subtypes, adenocarcinoma, squamous cell carcinoma, and large cell carcinoma -  Exclusion Criteria: None