Can PET scans reveal which stomach cancers will respond to immunotherapy?

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

Inclusion Criteria: 1. Age: 18 years ≤ age ≤ 80 years. 2. The subject must have histopathologically confirmed gastric adenocarcinoma via gastroscopic biopsy. 3. Clinical stage: cT3-4aN0-3M0 (according to the 8th edition UICC gastric cancer cTNM) with surgically resectable locally advanced gastric cancer, or cT3-4bN1-3M1 (non-peritoneal metastasis) with advanced gastric cancer. 4. Eastern Cooperative Oncology Group (ECOG) performance status score: 0-1. 5. Hematology: white blood cell count \> 4 × 10⁹/L, neutrophil count \> 2 × 10⁹/L, hemoglobin \> 90 g/L, and platelet count \> 100 × 10⁹/L. 6. Cardiac function: left ventricular ejection fraction (LVEF) \> 50%. 7. Liver function: total bilirubin \< 1.5 × the upper limit of normal (ULN); aspartate aminotransferase (AST) and alanine aminotransferase (ALT) \< 1.5 × ULN. 8. Renal function: serum creatinine ≤ 1.5 × ULN, or estimated glomerular filtration rate (eGFR) \> 60 mL/min. 9. The subject must agree to participate in this clinical trial and sign the informed consent form. 10. The subject must demonstrate good compliance, commit to adhering to the study procedures, and cooperate with the full implementation of the study process. 11. The subject must have no plans for pregnancy within 6 months. Exclusion Criteria: 1. Patients with other primary malignancies within 5 years, with the exception of adequately treated basal cell carcinoma and squamous cell carcinoma of the skin. 2. Patients with known hypersensitivity or contraindications to chemotherapeutic or immunotherapeutic agents. 3. Patients with severe concomitant diseases that, in the investigator's judgment, render the patient unsuitable for enrollment in this clinical study, including but not limited to severe cardiopulmonary insufficiency, severe bone marrow suppression, and severe hepatic or renal dysfunction. 4. Patients with severe psychiatric disorders, or those who are mentally impaired and unable to cooperate with the required study assessments. 5. Women who are pregnant, possibly pregnant, or breastfeeding. 6. Patients with poor compliance.