Short Course Radiotherapy With Sequential Disitamab Vedotin Combined With S-1 and Sintilimab as Whole Course Neoadjuvant Therapy for HER2 Expressed Locally Progressive Gastric Cancer

"Short range radiotherapy, PCTV (clinical planned target area) DT 25Gy/5F, once a day, for a total of 5 days, continuous irradiation, and IMRT (intensity modulated radiation therapy) technology; After a week of rest, radiotherapy and chemotherapy combined with immunotherapy will be performed~* Disitamab Vedotin: 2.5 mg/kg, intravenous infusion, d1, Q3W;~* Sintilimab: 200mg, iv;~* S-1: 40 mg/dose, oral, bid, d1-14; Q3W Whether to undergo adjuvant therapy after surgery is determined by the researcher"