Septum-guided Segmentectomy for 2-3 cm Clinical Stage IA3 Peripheral Non-Small Cell Lung Cancer

This is a single-center, prospective, single-arm, open-label clinical trial evaluating the efficacy and safety of septum-guided segmentectomy in patients with 2-3 cm clinical stage IA3 peripheral non-small cell lung cancer (NSCLC) with a consolidation-to-tumor ratio (CTR) greater than 0.5 and up to 1.0. All eligible participants will undergo planned septum-guided anatomical segmentectomy or combined segmentectomy after intraoperative frozen-section confirmation of node-negative (N0) lymph node status. The primary endpoint is 3-year recurrence-free survival (RFS).

Inclusion Criteria: * Age 18 to 80 years, male or female. * Clinical stage IA3 non-small cell lung cancer according to the International Association for the Study of Lung Cancer 9th edition tumor, node, metastasis classification; clinical T1cN0M0; tumor maximum diameter \>2 cm and \0.5 and \=60% predicted and single-breath diffusing capacity of the lung for carbon monoxide \>=60% predicted, unless otherwise documented after multidisciplinary evaluation. * Willing to undergo intraoperative lymph node frozen-section biopsy to confirm node-negative status and understands that a positive frozen-section result will lead to conversion to lobectomy as standard treatment and exclusion from the primary efficacy analysis. * Able to understand the study and voluntarily sign written informed consent. Exclusion Criteria: * Intraoperative lymph node frozen-section biopsy confirms N1 or N2 metastasis, or preoperative endobronchial ultrasound-guided biopsy or mediastinoscopy confirms N1, N2, or N3 metastasis, pleural dissemination, or distant metastasis. Patients with positive intraoperative frozen-section results will be converted to lobectomy plus systematic lymph node dissection as standard treatment and recorded as screen failures. * Multiple primary lung cancers or multiple pulmonary nodules requiring concurrent resection outside the protocol-defined scope that would affect assessment of the primary endpoint. * Prior ipsilateral lobectomy or segmentectomy, or severe pleural adhesions making the study procedure unevaluable. * Other active malignancy within 5 years, except cured low-risk tumors. * Severe cardiac, cerebral, hepatic, renal, or other disease that would preclude general anesthesia or curative lung cancer surgery. * Pregnant or breastfeeding women. * Any other condition that, in the investigator's opinion, makes the participant unsuitable for this study.