The Role of 18F-FDG&68Ga-FAPI PET/CT in the Assessment of Conversion Therapy Efficacy in Gastric Cancer with Peritoneal Metastasis.

If the target population of the study agrees to participate in the study, we will number the participants, resume their pathology files, and collect their gender, age, phone number, height and weight information, record the participants' consultation process and the results of the tests and examinations therein. During the course of the study we will perform 18F-FDG & 68Ga-FAPI PET/CT according to the participant's stage of disease, specifically: one 18F-FDG PET/CT prior to conversion therapy and one 68Ga-FAPI PET/CT as a baseline assessment. One 18F-FDG PET/CT and one 68Ga-FAPI PET/CT were performed before the clinician assessed that the conversion therapy was ready to be completed and the conversion surgery was about to be performed, and if the participant experienced a postoperative recurrence of the disease during the study period, another 18F-FDG PET/CT and a 68Ga-FAPI PET/CT would be performed, meaning that a total of 4 PET/CTs were performed. In other words, a total of 4 PET/CT visualizations were required for all participants; 2 additional PET/CT visualizations, including 18F-FDG PET/CT and 68Ga-FAPI PET/CT, were performed if the disease recurred after the conversion surgery, and none were required for participants without recurrence.

Inclusion criteria

• Histologically confirmed gastric adenocarcinoma with no history of resection of primary or metastatic lesions
• Peritoneal metastases of gastric cancer requiring laparoscopy for definitive diagnosis without gastric outflow tract obstruction and intestinal obstruction
• Patients voluntarily enrolled in this study by signing an informed consent form
• Age ≥ 18 years
• Eastern Cooperative Oncology Group (ECOG) score ≤ 2,
• Expected life expectancy ≥ 3 months
• Adequate organ and bone marrow function
• Willingness to adhere to the study protocol and follow-up programme

Exclusion criteria

• Signs of distant metastases other than peritoneal metastases at enrolment
• Pregnant or breastfeeding women.
• Patients with a history of other malignant diseases in the last 5 years, except cured skin cancer and carcinoma in situ of cervix
• Severe mental disease, uncontrolled epilepsy, or central nervous system disease