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

Lobectomy has long been the standard surgical treatment for operable early-stage non-small cell lung cancer (NSCLC). Randomized studies such as Japan Clinical Oncology Group 0802/West Japan Oncology Group 4607L (JCOG0802/WJOG4607L) and Cancer and Leukemia Group B 140503 (CALGB 140503) have supported sublobar resection for selected early-stage peripheral NSCLC, but most evidence is concentrated in tumors measuring 2 cm or less. For patients with 2-3 cm, solid-predominant clinical stage IA3 peripheral NSCLC, prospective evidence on the oncologic safety and pulmonary function benefit of segmentectomy remains limited. septum-guided segmentectomy uses the intersegmental vein and intersegmental septal membrane as anatomical landmarks to standardize the intersegmental plane and achieve reproducible anatomical resection while preserving lung function. This study uses a single-arm objective performance criterion design. The planned enrollment is 100 participants, allowing for approximately 15% unevaluable or lost-to-follow-up participants, with a target evaluable sample of 83. Before proceeding with segmentectomy, intraoperative frozen-section biopsy of protocol-specified lymph node stations is required to confirm node-negative (N0) disease. A positive frozen-section result will lead to conversion to lobectomy plus systematic lymph node dissection as standard treatment, and the participant will be recorded as a screen failure for the primary efficacy analysis while contributing to safety follow-up as specified in the protocol. Participants will be followed after surgery at 1, 6, 12, 18, 24, 30, and 36 months, and annually during years 4 and 5. The primary endpoint is 3-year recurrence-free survival (RFS). Secondary and safety outcomes include pulmonary function changes, perioperative outcomes, microscopically margin-negative (R0) resection, lymph node assessment, local recurrence, overall survival, disease-free survival, quality of life, and postoperative adjuvant therapy.