Based on existing literature, we posit that a leucine-restricted diet is safe and well-tolerated in patients with advanced gastric cancer receiving combined chemotherapy and immunotherapy. Patients adhering to this dietary regimen exhibit a significant reduction in serum leucine concentrations, with no notable impact on the serum levels of other amino acids. Furthermore, leucine restriction promotes the activation of immune cells within the tumor microenvironment. When applied in conjunction with chemotherapy and immunotherapy for advanced gastric cancer, this approach demonstrates synergistic anti-tumor efficacy. It is expected to enhance tumor response rates , improve the 1-year survival rate, prolong overall survival (OS), and ultimately optimize patient prognosis.
Diagnosis and Treatment Plan: Patients with advanced gastric cancer with distant metastasis, confirmed by imaging modalities (such as CT or PET-CT) and clinical pathological data, who are indicated for combined chemotherapy and immunotherapy.
Demographics: Aged 18 to 70 years, regardless of gender.
Dietary Capability: Capable of oral intake or receiving liquid diet via nasogastric tube.
Consent: Willing to participate in this study and have signed the Informed Consent Form (ICF).
Cognitive or Psychiatric Impairment: Cognitive dysfunction or psychiatric disorders that prevent the patient from understanding the study content or providing informed consent.
Diabetes Mellitus: Diagnosis of Type 1 or Type 2 diabetes mellitus.
Gastrointestinal Conditions: Presence of severe diarrhea, intractable vomiting, severe malabsorption syndrome, paralytic or mechanical intestinal obstruction, or active gastrointestinal bleeding.
Allergy：Known hypersensitivity or allergy to any of the main components of the leucine-deficient nutritional powder.
Single group
Lucine-restricted diet
Dietary supplementDuring each hospitalization cycle for combined chemotherapy and immunotherapy, study participants will undergo a 3-day leucine-restricted diet concurrently with PD-1 inhibitor and chemotherapy administration; following this 3-day intervention period, the dietary restriction will be discontinued, and patients will gradually resume a normal diet.
Response Evaluation Criteria in Solid Tumors (RECIST) Grade
This scoring system includes four grades: CR, PR, PD, and SD, where CR stands for complete response, PR for partial response, PD for progressive disease, and SD for stable disease.
1-year survival rate and overall survival (OS)
This indicator is calculated by comprehensively summarizing the 1-year survival rate and overall survival.
The tumor regression grade (TRG) system
TRG (Tumor Regression Grade) is used to assess pathological response after neoadjuvant therapy based on the 8th edition AJCC/CAP criteria. Different grades represent varying degrees of regression: TRG 0 indicates complete response (no residual tumor cells); TRG 1 indicates near-complete response (scattered residual tumor cells, \<10%); TRG 2 indicates partial response (residual tumor cells accounting for 10%-50%); TRG 3 indicates no or minimal response (residual tumor cells \>50%). Higher grades suggest poorer treatment efficacy.
Grade of CTCAE grading system
This indicator was assessed using the Common Terminology Criteria for Adverse Events (CTCAE) grading system, which comprises five grades (1-5). Grade 1 represents no or mild symptoms, while Grade 5 indicates death.
Changes in the Immune Microenvironment of Gastric Cancer Patients Following a Leucine-Restricted Diet
Comparative analysis of tumor scRNA-seq and ctDNA profiles pre- and post-diet, alongside flow cytometry-based assessment of circulating CD8+ T cells and ctDNA levels in blood samples.
Serum concentrations of various amino acids, including leucine, in patients with gastric cancer
Peripheral blood was collected for the determination of amino acid concentrations.
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