• overall survival [ Time Frame: 5 years ]
  To evaluate the 5 year overall survival (OS) rate of two groups.
• Pulmonary function [ Time Frame: 6 months and 12 months ]
  to evaluate the pulmonary function as measured by expiratory flow rate of the two groups 6 months and 12 months postoperatively.
• the duration of postoperative hospital stay [ Time Frame: an expected average of 5 days ]
  to evaluate the postoperative inpatient days of the two groups.
• performance status [ Time Frame: 12 months ]
  to evaluate the postoperative performance status of the two groups by ECOG score standard.

Objective: To compare the outcomes(including 5 year relapse free survival rate, 5 year overall survival rate, retaining pulmonary function and the rates of loco-regional and systemic recurrence ) of patients with peripheral stage IA (≤ 2 cm) non-small cell lung cancer undergoing anatomic segmentectomy vs lobectomy. And to evaluate whether the anatomic segmentectomy is an optimal type of surgery for the patients with peripheral stage IA (≤ 2cm) non-small cell lung cancer (NSCLC).

Outline: This is a multicenter, prospective, randomized open phase III study of anatomic segmentectomy vs lobectomy for the patients with peripheral stage IA (≤ 2cm) non-small cell lung cancer (NSCLC). According to completely random block design, the patients are randomized to 1 of 2 treatment arms.

• Arm I: Patients undergo anatomic segmentectomy by minimal incision thoracotomy or thoracoscopy/VATS.
• Arm II: Patients undergo lobectomy by minimal incision thoracotomy or thoracoscopy/VATS.

Patients will be followed up every 3 months for the first year and then every 6 months for the subsequent 2 years and annually for 5 years postoperatively.

• Experimental: segmentectomy
  Patients undergo anatomic segmentectomy by minimal incision thoracotomy or thoracoscopy/VATS.
  Intervention: Procedure: segmentectomy
• Active Comparator: lobectomy
  Patients undergo lobectomy by minimal incision thoracotomy or thoracoscopy/VATS.
  Intervention: Procedure: segmentectomy

Inclusion Criteria:

1. Age 18-70y

2. Preoperative criteria:

   ⅰ)Center of tumor is located in the outer third of the lung field, and the maximal diameter ≤ 2 cm(including coronal, traverse and sagittal view) confirmed by 1mm thin layer contrast-enhanced CT scan.

   ⅱ)no hilar and mediastinal lymph node metastasis verified by mediastinoscope/EBUS.

3. Intraoperative criteria:

   ⅰ)Adenocarcinama or squamous cell carcinoma of lung confirmed by frozen section.

   ⅱ)Lobectomy, single segmentectomy or combined segmentectomy is feasible.

   ⅲ)Confirmation of N0 status by frozen section examination of nodal levels 10 and 13 for segmentectomy, and 10 for lobectomy.

4. ECOG performance status 0-2.
5. No other malignancy within the past 3 years( except for well prognostic malignancy such as basal cell carcinoma of skin, superficial bladder cancer, or carcinoma in situ of the cervix).
6. No prior ipsilateral thoracotomy (prior diagnostic thoracoscopy is allowed).
7. No prior chemotherapy or radiation therapy.
8. Lobectomy is tolerated.
9. Sufficient organ functions.
10. Written informed consent.

Exclusion Criteria:

1. Active bacterial or fungous infection.
2. Simultaneous or metachronous (within the past 5 years) multiple cancers.
3. Interstitial pneumonitis, pulmonary fibrosis, or severe pulmonary emphysema, and can not tolerate lobectomy.
4. Psychosis.
5. Uncontrollable diabetes mellitus.
6. History of severe heart disease.
7. The maximal diameter of GGO≤5mm.
8. N1, N2, or M1a is confirmed postoperatively.
9. Postoperative adjuvant therapy (chemotherapy ,radiotherapy or targeted therapy).
10. Other types of lung cancer such as small cell lung cancer, large cell lung cancer, etc.
11. Confirmation of benign disease by postoperative pathologic examination.
12. Lesion located in the middle lobe.