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

Required: HER2 (ERBB2) expression (IHC1+, 2+, 3+) (IHC1+, 2+, or 3+)

IHC results confirm HER2 expression (defined as IHC1+, 2+, 3+)

Cannot have received: anti-HER2 therapy

Previously received the following therapies: anti-HER2

Cannot have received: anti-PD-1 therapy

Previously received the following therapies: anti-PD-1

Cannot have received: anti-PD-L1 therapy

Previously received the following therapies: anti-PD-L1

Cannot have received: anti-PD-L2 therapy

Previously received the following therapies: anti-PD-L2

Cannot have received: checkpoint inhibitor

drugs targeting another stimulus or synergistic inhibition of T cell receptors (including but not limited to CTLA-4, OX-40, CD137, etc.)

Cannot have received: systemic cytotoxic chemotherapy

Have not received systematic treatment for the current disease in the past, including anti-tumor radiotherapy, chemotherapy, immunotherapy, etc

Cannot have received: radiation therapy

Have not received systematic treatment for the current disease in the past, including anti-tumor radiotherapy, chemotherapy, immunotherapy, etc

Cannot have received: immunotherapy

Have not received systematic treatment for the current disease in the past, including anti-tumor radiotherapy, chemotherapy, immunotherapy, etc

Cannot have received: systemic traditional Chinese patent medicines and simple preparations with anti-tumor indications or drugs with immunomodulatory effect (thymosin, interferon, interleukin)

Exception: except for local use to control pleural effusion

Have received systematic systemic treatment with traditional Chinese patent medicines and simple preparations with anti-tumor indications or drugs with immunomodulatory effect (including thymosin, interferon, interleukin, except for local use to control pleural effusion) within 2 weeks before the first administration