Optimizing the Strategy for Preoperative Chemotherapy in Locally Advanced Gastric/Gastroesophageal Cancer

This is a randomized, phase II, open-label study. The purpose of this study is to determine the optimal treatment for patients with locally advanced Gastric/Gastroesophageal Cancer according to their HER-2 expression status.

The primary endpoint of this study: major pathology response rate the second endpoints of this study: pathology complete response rate R0 resection rate Progression-free survival ( PFS) Disease -free survival (DFS) Overall survival(OS) Objective response rate(ORR) Adverse event(AE)

(HER2, human epidermal growth factor receptor-2) positive patients: After 4 cycles of SOX±Trastuzumab neoadjuvant therapy, patients will continue to accept D2 surgery. The patients with R0 resection will continue to receive 4 cycles of SOX±Trastuzumab adjuvant chemotherapy. If the patients are confirmed with tumor progression before surgery, the treatment such as gastrectomy, chemoradiotherapy or second line chemotherapy should be determined by MDT team.

(HER2, human epidermal growth factor receptor-2,HER2) negative patients： After 4 cycles of DOS or SOX regimen as neoadjuvant therapy, patients will continue to accept D2 surgery. The patients with R0 resection will continue to receive then 4 cycles of DOS or SOX adjuvant chemotherapy. If the patients are confirmed with tumor progression before surgery, the treatment such as gastrectomy, chemoradiotherapy or second line chemotherapy should be determined by MDT team.

Eligibility Criteria:
Inclusion criteria:

1. Pathologically confirmed gastric cancer or gastroesophageal junction adenocarcinoma;
2. The HER2 receptor protein status should be assessed using immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH);

   * HER2 positive: IHC 3+ or IHC 2+/ FISH amplification.
   * HER2 negative: IHC 0, 1+ or IHC 2+/ FISH without amplification.
3. T3-4, any N stage, M0 of gastric or gastro-esophageal junction adenocarcinoma;
4. Chemotherapy and radiotherapy naïve.
5. Age ≥18 years;
6. ECOG(Eastern Cooperative Oncology Group ) 0-1;
7. Adequate hematological, hepatic and renal functions: absolute neutrophil count (ANC) ≥ 2.0 G/L, hemoglobin ≥ 90g/L, platelet ≥ 100 G/L; ALT and AST \<1.5 times x upper limit of normal (ULN)；serum total bilirubin \< 1.0 x ULN; serum creatinine \< 1.0 x ULN;
8. Left ventricular ejection fraction\>50%
9. Written informed consent.

Exclusion criteria:

1. Other pathology Type Other than adenocarcinoma, such as squamous cell carcinoma
2. History of allergies to drugs in the study
3. Intraperitoneal dissemination or distant metastasis
4. Digestive tract obstruction or uncontrollable recurrent bleeding ,clinical significant ascites
5. Dysphagia
6. Any cause of cirrhosis
7. Cardiac function NYHA(New York Heart Association) \>I degrees
8. Previous myocardial infarction, unstable angina, stroke ,or uncontrollable Arrhythmia
9. Any surgical contraindication
10. Any chemotherapy or radiotherapy history
11. Any surgical resection history of gastric cancer
12. History of any other tumors except cured cutaneum carcinoma or carcinoma in situs of cervix
13. Any contraindication for chemotherapy