The main purpose of this study is to evaluate the reasonable range of No.12a lymph node dissection of locally advanced gastric cancer.

Inclusion Criteria:

• ≥ 18 and ≤ 75 years of age; Preoperative gastric cancer patients with pathologically confirmed; Had been treated with Radical resection (D2, R0) of gastric cancer (Lymph node≥16); Willing and able to comply with the program during the study period; Physical condition and organ function allows to tolerable abdominal surgery; Written informed consent provided; Under radical laparoscopic distal subtotal gastrectomy With more than a 6-month life expectancy; No other serious concomitant diseases; Sufficient organ functions; No previous history of chemotherapy or radiotherapy; Clinical stage: T2-4aNxM0; Karnofsky performance status (KPS)>60; Eastern Cooperative Oncology Group Performance Status (ECOG): 0-1.

Exclusion Criteria:

• Pregnancy or breast feeding; Patients with Serious liver disease (such as cirrhosis, etc.), kidney disease, respiratory disease or uncontrolled diabetes, hypertension and other chronic systemic diseases, heart disease with Clinical symptoms, such as congestive heart failure, coronary heart disease symptoms, drug is difficult to control arrhythmia, hypertension, or six months had a myocardial infarction attack, or cardiac insufficiency; Organ transplantation patients need immunosuppressive therapy; Severe recurrent infections were not controlled or with other serious concomitant diseases; Patients got other primary malignant tumors (except curable skin basal cell carcinoma and cervical cancer in situ) except gastric cancer within 5 years; Psychiatric disease which require treatment; Have the history of organ transplantation; Within 6 months before study starts and in the process of this study, patients participate in other clinical researches.

100 patients with advanced gastric cancer，underwent radical laparoscopic distal gastrectomy. Observation of lymph node metastasis in different No.12a subgroups.