Noninvasive Detection of Lung Nodule Malignancy Using cfDNA Fragmentomics

Inclusion Criteria: * Age ≥ 18 years; * Positive for lung nodules on low-dose spiral CT (LDCT) meeting one of the following criteria: Solid or part-solid nodules ≥ 5 mm and ≤ 20 mm; Pure ground-glass nodules ≥ 8 mm and ≤ 30 mm; In cases of multiple nodules, the largest nodule (by maximum diameter) must meet these criteria; * Participants whose lung nodule status (benign or malignant) can be clinically confirmed; * No cancer-directed therapy (e.g., chemotherapy, radiotherapy, immunotherapy, cell therapy) within the past 3 months; * Able to provide a 5 mL peripheral blood sample prior to any treatment; * Voluntary signing of informed consent after full explanation of the study. Exclusion Criteria: * Pregnant or breastfeeding; * Current or past diagnosis (within the past 5 years) of malignant tumors (excluding patients with early-stage lung cancer who have undergone surgery but still have multiple evaluable nodules), or with severe heart disease, serious liver or kidney disorders, or significant bone marrow hematopoietic dysfunction; * History of organ transplantation or blood transfusion within the past 3 months; * History of seropositivity for human immunodeficiency virus (HIV); * Any other condition deemed inappropriate for study participation by the investigators.