Comparison of Segmentectomy Versus Lobectomy for Non-small Cell Lung Cancer ≤ 2 cm in the Middle Third of the Lung Field

Inclusion Criteria: 1. Patient aged 18-75 years old; 2. 6 mm ≤ tumor size ≤ 20 mm; 3. 0.25 \< CTR \< 1; 4. Center of tumor located in the middle third of the lung field; 5. ECOG score of 0,1 or 2; 6. Lung function (FEV1 ≥ 1 L and ≥ 70%); 7. Both lung segmentectomy and lobectomy could achieve R0 resection; 8. No serious cardiopulmonary complications, and could withstand both lung segmentectomy and lobectomy; 9. No hilus pulmonis and mediastinal lymph node metastasis and no distant metastasis; 10. Single tumor nodule or the concomitant nodule \< microinvasive tumor; 11. Written informed consent. Exclusion Criteria: 1. The tumor nodule is located in right middle lobe; 2. A history of other malignancies in the last 5 years (exclusion of early-staged thyroid cancer); 3. Have received preoperative anti-tumor therapy, including prior chemotherapy, radiation therapy, target therapy and so on; 4. A serious mental illness; 5. Pregnant and lactating women; 6. Congestive heart failure, myocardial infarction, severe stenosis of coronary artery within recent 6 months; 7. With the history of cerebral infarction or cerebral hemorrhage within 6 months; 8. With the history of sustained systemic corticosteroid therapy within 1 month; 9. The predicted surgical margin is less than 2 cm or the maximum diameter of the tumor at the 3D-CTBA 10. Other unsuitable situations;