This prospective clinical observational study aims to construct a metabolite database specifically for gastric cancer patients using metabolomics technology. It seeks to develop and validate metabolic biomarkers for early diagnosis, prognosis, and prediction of recurrence and metastasis in gastric cancer, thereby a establishing safe, convenient, and highly sensitive method for early screening and prognostic prediction.

Inclusion Criteria:

• **Healthy Controls:**

  1. Age > 18 years;
  2. Signed informed consent and willingness to participate in the project.

**Gastric Cancer:**

1. Age ≥ 18 years;
2. Performance status (ECOG) score ≤ 1;
3. Histopathologically confirmed gastric adenocarcinoma;
4. No family history of hereditary cancer;
5. No prior anti-tumor treatment;
6. Availability of primary tumor tissue from surgery or biopsy that meets submission requirements;
7. Availability of peripheral blood samples that meet submission requirements;
8. Willingness and ability to sign the informed consent form to participate in the study.

Exclusion Criteria:

• **Healthy Controls:**

  1. Individuals at high risk for hereditary colorectal adenocarcinoma, including family members of the following diseases: family history of gastrointestinal tumors, familial adenomatous polyposis (FAP), hereditary nonpolyposis colorectal cancer (HNPCC/LS), and Peutz-Jeghers syndrome (P-J syndrome);
  2. History of chronic metabolic or inflammatory diseases that are difficult to control, such as hypertension, diabetes, chronic viral hepatitis, and inflammatory bowel disease;
  3. Known history of other malignancies that have progressed or required treatment within the past 5 years, except for skin basal cell carcinoma and squamous cell carcinoma that have been cured;
  4. History of oral or intravenous use of broad-spectrum antibiotics and probiotics within the past month;
  5. Regular use of immunosuppressive drugs within the past 6 months;
  6. Long-term use of other medications that may affect metabolism, such as hormones;
  7. Inability or unwillingness to cooperate with follow-up visits and related examinations;
  8. Inability to eat normally or requiring medications or enemas for bowel movements;
  9. Presence of psychiatric disorders or other severe cardiovascular diseases;
  10. Pregnant, breastfeeding, or planning to become pregnant within the next year;
  11. Currently participating in an interventional clinical study or receiving study treatment that may influence the patient's treatment decision.

**Gastric Cancer:**

1. Currently participating in an interventional clinical study or receiving study treatment that may influence the patient's treatment decision;
2. Known history of other malignancies that have progressed or required treatment within the past 5 years, except for skin basal cell carcinoma and squamous cell carcinoma that have been cured;
3. History of chronic metabolic or inflammatory diseases that are difficult to control, such as hypertension, diabetes, chronic viral hepatitis, and inflammatory bowel disease;
4. Presence of poorly controlled chronic comorbidities that may affect prognosis;
5. Presence of psychiatric disorders or other severe cardiovascular diseases;
6. Pregnant, breastfeeding, or planning to become pregnant within the next year;
7. Long-term use of medications that may affect metabolism, such as hormones, immunosuppressants, antibiotics, etc.;
8. Any severe and/or uncontrolled medical conditions, as judged by the investigator, that may affect the patient's ability to participate in the study or interfere with study results.

Patients with gastric cancer and healthy individuals.