Concurrent Chemoradiotherapy Combined With Sintilimab as Neoadjuvant Therapy for Advanced Gastric Cancer Patients With Para-aortic Lymph Node Metastasis: a Single-arm, Phase II, Exploratory Study.

This trial is a prospective, single arm, single center, phase II clinical study aimed at subjects with advanced gastric cancer and para aortic lymph node metastasis, exploring the feasibility and safety of Sintilimab Injection combined with synchronous chemo-radiotherapy as neoadjuvant therapy.

Patients will receive sintilimab Injection (200mg iv q3w d1) combined with concurrent radiotherapy and chemotherapy. The chemotherapy regimen will use oxaliplatin 130mg/m2+S-1 40mg/m2 bid d1-14. Radiotherapy is performed using intraperitoneal radiation therapy, once a day, five times a week, at a dose of 1.8-2 Gy/f, for a total of 45-50.4 Gy (60-66 Gy for lymph node lesions). Radiation therapy starts from the second cycle of Sintilimab Injection combined with chemotherapy. The subjects underwent imaging evaluation after completing 4 cycles of combination chemotherapy and radiation therapy with Sintilimab Injection. Evaluated as a surgical subject (surgical conditions: imaging evaluation of enlarged lymph nodes adjacent to the abdominal aorta with PR or no significant activity), radical surgery will be performed within 4 weeks after the last study drug treatment. After surgery, the researcher will determine the necessity of adjuvant treatment and develop an adjuvant treatment plan based on the subject's condition. Subjects evaluated as inoperable will have their best follow-up treatment plan determined by the researcher.