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.

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 <=3 cm on imaging evaluation.
• Consolidation-to-tumor ratio (CTR) >0.5 and <=1 on thin-section computed tomography.
• Peripheral tumor judged by the investigator to be amenable to curative segmentectomy or lobectomy, with an anticipated ability to achieve the protocol-specified surgical margin.
• Eastern Cooperative Oncology Group (ECOG) performance status 0 to 1.
• Preoperative pulmonary function adequate for surgery, with forced expiratory volume in 1 second >=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.