Only the study team can determine whether someone qualifies for participation.
Inclusion criteria
Age ≥ 18 years.
Histologically confirmed gastric or gastroesophageal junction adenocarcinoma.
Clinical stage cT3-4a, N+, M0 (locally advanced) assessed by CT/MRI and endoscopic ultrasound.
Scheduled to receive neoadjuvant chemotherapy combined with PD-1 inhibitors (regimens including but not limited to SOX/XELOX + Sintilimab/Tislelizumab/Camrelizumab, etc.) as standard of care.
Availability of standard pre-treatment contrast-enhanced abdominal CT images.
Willingness to provide peripheral blood samples and tumor tissue (biopsy/surgical) for sequencing and analysis.
ECOG performance status 0-1.
Adequate organ function to tolerate systemic chemotherapy.
Exclusion criteria
Evidence of distant metastasis (Stage IV) or unresectable disease.
Previous systemic anti-tumor therapy for gastric cancer (chemotherapy, radiotherapy, or immunotherapy).
History of other malignancies within the past 5 years.
Active autoimmune diseases requiring systemic immunosuppressive treatment (contraindication for PD-1 inhibitors).
Emergency surgery due to obstruction, perforation, or uncontrolled bleeding.
Severe metallic artifacts on CT images that interfere with radiomic feature extraction.
Pregnancy or lactation.