In this study, the investigators will use LM-302 and S-1 plus intraperitoneal paclitaxel with or without Cadonilimab to treat Claudin 18.2-positive gastric or gastroesophageal junction adenocarcinoma with peritoneal metastasis.
Histologically confirmed gastric or gastroesophageal junction adenocarcinoma with her 2 (-), and without the history of resection of primary or metastatic lesion;
Age ≥ 18 years at registration;
Peritoneal metastases from gastric cancer requiring definitive diagnosisby laparoscopy, and without gastric outflow tract obstruction andintestinal obstruction;
Claudin 18.2 positive (≥ 25%, moderate to strong staining);
Presence of distant metastases other than peritoneal metastasis at the time of enrollment;
Pregnant or breastfeeding women;
Prior treatment with Claudin 18.2 targeted therapy;
History of other malignancies within the past 5 years, except for cured skin cancer or cervical carcinoma in situ;