Anatomic segmentectomy may be a less invasive type of surgery than lobectomy for cT1aN0M0 peripheral NSCLC and may retain more pulmonary function. It is not yet known whether anatomic segmentectomy is non-inferior to lobectomy in treating stage IA non-small cell lung cancer. The aim of this study is to investigate whether the outcome of anatomic segmentectomy is similar to lobectomy for peripheral stage IA (≤ 2cm)non-small cell lung cancer (NSCLC).

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.

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.