Establishment of Serum Proteomics Subtypes of Gastric Cancer and Its Clinical Application

This study is a prospective, single-center, observational study aimed at detecting the status of serum protein profiles at key time points in gastric cancer patients receiving neoadjuvant therapy for advanced disease, and constructing a serum protein model for evaluating the efficacy of neoadjuvant therapy for gastric cancer. Subjects will receive neoadjuvant therapy (treatment regimen determined by the primary physician, limited to systemic therapy, with options including immune checkpoint inhibitor-based regimens and non-immune checkpoint inhibitor-based regimens). After four cycles of treatment, the efficacy will be assessed. Patients eligible for R0 resection will undergo D2 radical surgery regardless of tumor regression, while those ineligible for R0 resection will enter the palliative treatment phase (Note: Subjects are all patients who require neoadjuvant therapy even if they do not participate in this clinical study). Patients will receive regular follow-up evaluations for metastasis/recurrence and survival until tumor recurrence/progression or the last known date of patient survival (Note: Regular follow-up in this study follows the frequency of routine clinical follow-ups). The primary endpoint is progression-free survival (PFS), and the secondary endpoint is pathological response rate (based on Becker tumor regression grading, with residual tumor less than 50% considered effective preoperative treatment). Peripheral venous blood samples will be collected before the start of neoadjuvant therapy (blood sampling point 1 - baseline) and before surgery after neoadjuvant therapy (blood sampling point 2 - post-treatment). Approximately 3 ml of blood will be collected each time, and about 1.5 ml of serum will be obtained after processing. Serum protein profiling will be conducted to assess the expression of protein profiles at these treatment time points.