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

This is a prospective study conducted in three stages. The volume of blood drawn will be 30 mL each time. Stage 1: We will enroll 200 patients diagnosed with stage I-IIIB NSCLC who are scheduled for lobectomy and systematic lymph node dissection. The prediction of lymph node metastasis will be based on preoperative blood ctDNA mutation and methylation profiling. Specifically, during this stage, we will prospectively establish ctDNA methylation signatures specifically associated with LNMs in NSCLC. These molecular profiles will be combined with PET-CT imaging. Postoperative pathological results will serve as the reference standard for comparison. Stage 2: A certain number (depending on the Results of Stage 1) of patients requiring invasive mediastinoscopy or EBUS-TBNA, based on the clinical guidelines, will be included for blood ctDNA mutation/methylation profile (or combined PET-CT), and the detection rate of LNMs will be assessed in patients with negative preoperative blood ctDNA mutation/methylation (or combined PET-CT). The accuracy of predicting LNMs will be compared with that of patients with negative or positive preoperative blood ctDNA mutation/methylation (or combined PET-CT). Stage 3: For patients with negative preoperative blood negative testing (ctDNA mutation/methylation profiles alone or in combination with PET-CT), systematic lymph node sampling/dissection and no lymph node dissection will be grouped and compared. Regular follow-up is performed to investigate the impact on long-term MRD negative duration and prognosis. The primary outcomes: postoperative MRD negative duration and progression-free survival (PFS); The second outcomes: Overall survival (OS).