Effects of High-Fiber Diet on Gut Microbiota, Metabolism, and Immune Microenvironment in Solid Tumor Patients: A Clinical Study

Cancer remains a major global public-health challenge and a central focus of medical research. According to the International Agency for Research on Cancer (IARC, 2020), 19.29 million new malignant tumors and 9.96 million cancer deaths occurred worldwide, >90 % being solid cancers. Lung cancer alone accounted for 2.2 million new cases and 1.8 million deaths; >75 % of patients were already at an advanced stage at diagnosis. Current options for late-stage solid tumors are limited: surgery is often impossible because of metastasis; cytotoxic chemotherapy produces dose-limiting toxicities (grade Ⅲ-Ⅳ myelosuppression 15-40 %, mucositis 50-80 %); radiotherapy risks pneumonitis (5-15 %) or enteritis (5-20 %) when tumors abut vital organs; targeted agents succumb to acquired resistance after a median 9-13 months; and immune-checkpoint inhibitors achieve <40 % objective response with 7-15 % grade 3-4 immune-related adverse events.

Dietary intervention is therefore emerging as a promising adjunct. Dietary fibre protects against cardiovascular and metabolic diseases, yet intake is universally low. WHO and the Chinese Nutrition Society recommend 25-30 g total fibre per day (≈15-21 g insoluble), whereas Chinese adults consume only ~11 g insoluble fibre. High-fibre diets reshape gut microbiota, augment short-chain fatty acid (SCFA) production, strengthen intestinal barrier function, activate CD8⁺ T cells and dampen regulatory T cells, thereby enhancing anti-tumour immunity. A melanoma cohort showed improved progression-free survival under immunotherapy when fibre intake was high. Similar microbiota-immune axes may operate in colorectal and other solid cancers, but clinical data are scarce.

We therefore propose a study to examine whether a high-insoluble-fibre diet (>21 g/day) modulates gut-microbiota composition, metabolite profiles and peripheral-blood immune subsets in solid-tumour patients, and to evaluate consequent effects on treatment response and quality of life. The findings will clarify whether fibre-driven microbiota-immune crosstalk can be harnessed as a personalised nutritional strategy to improve cancer outcomes.

Study Overview

• Status: Recruiting
• Conditions: Diet Habits; Colorectal Cancer (Diagnosis); High-fibre Diet
• Intervention / Treatment: Dietary supplement: High-fibre diet

• Study Type: Interventional
• Enrollment (Estimated): 25
• Phase: Phase 1

Contacts and Locations

• Study Contact: Name: Jingwen Wei; Phone Number: 8283095730; Email: jingwenwinni@163.com

Study Locations

• China
  • Sichuan
    • Chengdu, Sichuan, China
      • Recruiting
      • West China Hospital
      • Contact: Jingwen Wei; Phone Number: 8283095730; Email: jingwenwinni@163.com

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

• (1) Sign a written informed consent form before any study - related procedures are carried out.

  (2) Males or females, aged 18 - 80 years old. (3) Diagnosed with solid tumors by pathological tissue biopsy. (4) According to the RECIST v1.1 (Response Evaluation Criteria in Solid Tumors Version 1.1) criteria, there is at least 1 measurable lesion (lesions previously treated with local therapies such as radiotherapy cannot be regarded as measurable lesions).

  (5) ECOG (Eastern Cooperative Oncology Group Performance Status) score of 0 - 1.

  (6) NRS - 2002 (Nutritional Risk Screening 2002) score < 3. (7) BMI (Body Mass Index) ≥ 18.5 (can be adjusted appropriately according to the actual situation).

  (8) Patients who can eat orally or through a feeding tube and can tolerate enteral nutrition.

  (9) Sufficient organ function, and the subjects need to meet the following laboratory indicators: In the absence of granulocyte - colony - stimulating factor use in the past 14 days, the absolute neutrophil count ≥ 1.5×10⁹/L.

Platelets ≥ 75×10⁹/L. In the absence of blood transfusion or erythropoietin use in the past 7 days, hemoglobin ≥ 8 g/dL.

Serum albumin ≥ 3.0 g/dL. Total bilirubin ≤ 1.5× the upper limit of normal (ULN). Aspartate Aminotransferase (AST) and Alanine Aminotransferase (ALT) ≤ 2.5×ULN. In case of liver metastasis, ALT and/or AST ≤ 5×ULN, and total bilirubin ≤ 3×ULN. In case of liver or bone metastasis, Alkaline Phosphatase (AKP) ≤ 5×ULN.

Creatinine clearance rate ≥ 50 mL/min (calculated according to the Cockcroft - Gault formula) or serum creatinine ≤ 1.5×ULN.

International Normalized Ratio (INR) ≤ 1.5×ULN, Prothrombin Time (PT) and Activated Partial Thromboplastin Time (APTT) ≤ 1.5×ULN.

Urine protein < 2+ (if urine protein ≥ 2+, a 24 - hour urine protein quantification can be performed, and subjects with a 24 - hour urine protein quantification < 2.0 g can be enrolled).

(10) Women of child - bearing potential must agree to avoid sexual intercourse (heterosexual intercourse) or use a reliable and effective contraceptive method from the signing of the informed consent form until at least 6 months after the last administration of the study drug. In addition, the serum HCG (Human Chorionic Gonadotropin) test must be negative within 3 days before the start of the study treatment, and the subject must be non - lactating. A female patient is considered to be of child - bearing potential if she is post - menopausal but has not reached the post - menopausal state (non - menstrual period ≥ 12 consecutive months, and no other causes are found except menopause) and has not undergone sterilization surgery (such as hysterectomy, bilateral tubal ligation, or bilateral oophorectomy).

(11) If there is a risk of pregnancy, all subjects (regardless of male or female) need to use a contraceptive method with an annual failure rate of less than 1% throughout the treatment period until 120 days after the last administration of the study drug (or 180 days after the last administration of the chemotherapy drug)

Exclusion Criteria:

• (1) Patients with cognitive impairment or mental illness who are unable to understand the study content.

  (2) Patients with central nervous system or meningeal metastases. (3) Patients with clinically symptomatic moderate or severe ascites (that is, those who require therapeutic paracentesis within 2 weeks before the start of study treatment; patients with only a small amount of ascites shown on imaging and no clinical symptoms can be enrolled).

  (4) Patients with uncontrolled or moderate to severe pleural effusion and pericardial effusion.

  (5) Patients with severe diarrhea, intractable vomiting, severe malabsorption syndrome, paralytic and mechanical intestinal obstruction; tracheoesophageal fistula, gastrointestinal perforation or gastrointestinal fistula, or abdominal abscess; patients with extra - gastrointestinal bleeding with a CTCAE (Common Terminology Criteria for Adverse Events) grade 3 or above within 6 months before the start of study treatment or grade 2 or above within 3 months (such as abnormal vaginal bleeding, hematemesis).

  (6) Patients known to be allergic to the active ingredients or excipients of the study drug.

  (7) Patients with poorly controlled diabetes. (8) Patients with poorly controlled hypertension (systolic blood pressure ≥ 140 mmHg and/or diastolic blood pressure ≥ 90 mmHg under routine antihypertensive treatment), with a history of hypertensive crisis or hypertensive encephalopathy.

  (9) Patients with severe cardiovascular and cerebrovascular diseases, including cerebrovascular accident (CVA), transient ischemic attack (TIA), myocardial infarction, and major vascular diseases within 6 months before enrollment (including but not limited to aortic aneurysms requiring surgical repair or recent arterial thrombosis); patients with poorly controlled clinical symptoms or heart diseases, such as unstable angina pectoris, NYHA (New York Heart Association) heart failure grade II or above, left ventricular ejection fraction < 50% on color Doppler echocardiography, or severe arrhythmias that cannot be controlled by drug treatment.

  (10) Pregnant or lactating women. (11) Other situations considered by the investigator as inappropriate for enrollment.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: N/A
• Interventional Model: Single Group Assignment
• Masking: None (Open Label)

Number of Arms

1

Arms and Interventions

Participant Group / Arm

Intervention / Treatment

Experimental: high-insoluble-fibre diet

Dietary supplement: High-fibre diet; Dietary fibre, recommended at 25-30 g/d (15-21 g insoluble), is chronically under-consumed (~11 g/d in China). High-fibre diets increase SCFAs, enhance gut-barrier integrity and boost anti-tumour immunity, correlating with better immunotherapy outcomes in melanoma. Clinical evidence in solid tumours is lacking. Our trial will test whether >21 g/d insoluble fibre reshapes microbiota, metabolites and immune markers in solid-cancer patients and improves treatment response and quality of life, providing rationale for microbiota-targeted nutrition.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Evaluate the safety and tolerability of High-fibre diet in patients with solid tumors.	The occurrence types, frequencies, and severities of treatment - emergent adverse events (TEAE).	From enrollment to the end of treatment at 6 weeks

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Objective Response Rate (ORR)	Evaluate the effectiveness of arginine - restricted diet in patients with solid tumors.	From enrollment to the end of treatment at 1 year
Disease Control Rate (DCR)	Evaluate the effectiveness of arginine - restricted diet in patients with solid tumors.	From enrollment to the end of treatment at 1 year
Duration of Response (DoR)	Evaluate the effectiveness of arginine - restricted diet in patients with solid tumors	From enrollment to the end of treatment at 1 year

Collaborators and Investigators

• Sponsor: West China Hospital

Study record dates

Study Major Dates

• Study Start (Actual): October 31, 2025
• Primary Completion (Estimated): June 30, 2026
• Study Completion (Estimated): June 30, 2026

Study Registration Dates

• First Submitted: March 12, 2026
• First Submitted That Met QC Criteria: March 12, 2026
• First Posted (Actual): March 17, 2026

Study Record Updates

• Last Update Posted (Actual): March 17, 2026
• Last Update Submitted That Met QC Criteria: March 12, 2026
• Last Verified: October 1, 2025

More Information

Terms related to this study

• Keywords: Colorectal Cancer; high-fibre diet
• Additional Relevant MeSH Terms: Pathologic Processes; Neoplasms by Site; Neoplasms; Intestinal Diseases; Gastrointestinal Neoplasms; Digestive System Neoplasms; Digestive System Diseases; Gastrointestinal Diseases; Intestinal Neoplasms; Rectal Diseases; Colonic Diseases; Pathological Conditions, Signs and Symptoms; Behavior; Behavior, Animal; Colorectal Neoplasms; Disease; Feeding Behavior
• Other Study ID Numbers: Approval No. 1038 (2025)

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No