Predicting Non-small Cell Lung Cancer (NSCLC) Lymph Node Metastasis: Integrating Circulating Tumor DNA (ctDNA) Mutation/ Methylation Profiling With Positron Emission Tomography-computed Tomography (PET-CT) Scan

Inclusion Criteria: 1. Provision of informed consent prior to study initiation. 2. Age between 18 and 75 years. 3. Preoperative clinical evaluation indicating non-small cell lung cancer (NSCLC) stage I-IIIB (without initial treatment sought). 4. Newly treated patients who have consented to undergo surgery. 5. Eastern Cooperative Oncology Group (ECOG) performance status (PS) score of 0-1. Exclusion Criteria: 1. Non-small cell lung cancer (NSCLC) histopathologically determined to be other than stage I-IIIB following surgical evaluation. 2. Presence of other active malignant tumor diseases. 3. Evidence of any serious or uncontrolled systemic illness, including uncontrolled hypertension and active bleeding, as assessed by the investigator, which may contribute to reluctance to participate in the trial or decrease adherence to the study regimen. Additionally, active infectious diseases such as hepatitis B, hepatitis C, and human immunodeficiency virus (HIV) infection are grounds for exclusion. 4. History of interstitial lung disease (ILD), drug-induced ILD, radiation pneumonitis requiring steroid therapy, or any indication of clinically active ILD. 5. Patients considered by the investigator to be unable to comply with the study protocol, restrictions, and requirements, or those facing circumstances at the investigator's discretion that would impede their participation in the study.