Fiber-Boost Randomized Controlled Trial (Fiber-Boost)

March 16, 2026 updated by: Maximilian Boesch, Cantonal Hospital of St. Gallen

Multicenter, Randomized, Controlled Trial to Study the Effects of a High-Fiber Dietary Intervention on ctDNA Clearance and the Microbial and Immunological Landscape in Patients With Advanced Non-Small Cell Lung Cancer Receiving PD-1/PD-L1-Targeted Monotherapy (Fiber-Boost)

In the present study 'Fiber-Boost', we investigate how a high-fiber diet affects the immunotherapy of advanced lung cancer and what effects it has on the gut microbiome (i.e., the bacteria in the gut) as well as the immune system. Study participants will be assigned to either a test group or a control group. Only patients in the test group will undergo a high-fiber diet. The study lasts 6 weeks per patient and will be conducted at 4 centers within Switzerland. A total of 42 patients are planned to be included in the study.

Study Overview

Status

Status

Indicates the current recruitment status or the expanded access status.
Recruiting

Conditions

Conditions

The disease, disorder, syndrome, illness, or injury that is being studied. On ClinicalTrials.gov, conditions may also include other health-related issues, such as lifespan, quality of life, and health risks.

Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.

Detailed Description

The activity of immune checkpoint blockade (ICB) mechanistically depends on the host microbiome and is manipulable through diet. In this study termed Fiber-Boost, we propose a multicenter trial of a supplement-based high-fiber diet (HFD) in non-small cell lung cancer (NSCLC) treated with first-line ICB monotherapy. Using a randomized, controlled design, we mechanistically explore the role of dietary fibers in cancer immunotherapy. Circulating tumor DNA (ctDNA) quantification as well as a rich pipeline of companion microbiome and immune profiling technologies will improve the understanding of the diet-microbiome-immune axis in therapeutic anticancer immunity and treatment response. The overarching goal is to elucidate novel therapeutic strategies for ICB sensitization in NSCLC using microbiome-centered, non-pharmaceutical interventions. Sex and gender dimensions are biologically not sufficiently relevant for the current study to merit corresponding stratification or analyses.

Study Type

Study Type

Describes the nature of a clinical study. Study types include interventional studies (also called clinical trials), observational studies (including patient registries), and expanded access.
Interventional

Enrollment (Estimated)

Enrollment

The number of participants in a clinical study. The "anticipated" enrollment is the target number of participants that the researchers need for the study.
42

Phase

Phase

The stage of a clinical trial studying a drug or biological product, based on definitions developed by the U.S. Food and Drug Administration (FDA). The phase is based on the study's objective, the number of participants, and other characteristics. There are five phases: Early Phase 1 (formerly listed as Phase 0), Phase 1, Phase 2, Phase 3, and Phase 4. Not Applicable is used to describe trials without FDA-defined phases, including trials of devices or behavioral interventions.
  • Not Applicable

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

Study Contact

The name and contact information for the person who can answer enrollment questions for a clinical study. Each location where the study is being conducted may also have a specific contact, who may be better able to answer those questions.

Study Locations

  • Switzerland
      • Basel, Switzerland, 4031
        • Not yet recruiting
        • Universitätsspital Basel
        • Contact:
      • Chur, Switzerland, 7000
        • Not yet recruiting
        • Kantonsspital Graubunden
        • Contact:
      • Sankt Gallen, Switzerland, 9007
        • Recruiting
        • HOCH Health Ostschweiz, Cantonal Hospital St.Gallen
        • Contact:
      • Winterthur, Switzerland, 8401
        • Not yet recruiting
        • Kantonsspital Winterthur
        • Contact:

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Eligibility Criteria

The key requirements that people who want to participate in a clinical study must meet or the characteristics they must have. Eligibility criteria consist of both inclusion criteria (which are required for a person to participate in the study) and exclusion criteria (which prevent a person from participating). Types of eligibility criteria include whether a study accepts healthy volunteers, has age or age group requirements, or is limited by sex.

Ages Eligible for Study

  • Adult
  • Older Adult

Accepts Healthy Volunteers

No

Description

Inclusion Criteria:

  • Age ≥18 years
  • Written informed consent according to Swiss law and ICH/GCP regulations before inclusion and prior to any trial-specific procedures
  • Histologically or cytologically confirmed NSCLC
  • Advanced or recurrent NSCLC not amenable to curative treatment
  • PD-L1 expression ≥50% (TPS) determined by an approved IHC test
  • No actionable genetic alterations in genes such as EGFR, ALK, ROS1, HER2, BRAF, RET, MET, NTRK
  • First-line palliative PD-1/PD-L1-targeted monotherapy at a 3-weekly schedule indicated per local investigator
  • Willingness and ability to undergo study interventions
  • ECOG performance status 0-2
  • Adequate organ function:
  • Hemoglobin ≥70 g/L, platelet count ≥50 G/L, granulocytes ≥1 G/L
  • Bilirubin, ALT, AST ≤3 x ULN
  • Glomerular filtration rate (Cockroft-Gault) ≥30 mL/min/1.73m²
  • Measurable or evaluable disease per RECIST 1.1
  • Patients with CNS metastases are eligible, provided there is no requirement for corticosteroids as therapy for CNS disease and no evidence of clinical progression
  • Women with child-bearing potential use effective contraception (two independent methods), are not currently pregnant or lactating, and agree to not become pregnant during the trial treatment and during 3 months thereafter. A negative pregnancy test in either urine or blood is required for women with child-bearing potential before trial inclusion.
  • Men who are not sterile agree to use contraceptive methods (condoms) or abstain from sexual intercourse during the trial treatment and 3 months thereafter.

Exclusion Criteria:

-History of malignancy, unless in remission for at least 3 years before inclusion with the exception of pT1-2 prostate cancer Gleason score <6, adequately treated cervical carcinoma in situ or localized non-melanoma skin cancer

Adjuvant or additive systemic ICB treatment within 6 months prior to inclusion

  • Systemic treatment with an antibiotic within 10 days of ICB treatment/HFD intervention start
  • Concomitant immunosuppressive drugs including corticosteroids at a daily dose of ≥10mg prednisone equivalents, methotrexate, azathioprine, TNF-α inhibitors
  • Concurrent treatment with other experimental drugs or other anticancer therapy
  • Major surgical procedures within 14 days prior to inclusion as judged by the investigator
  • Active autoimmune disease requiring systemic immunosuppressive treatment that is seen as contraindication for the use of PD-1/PD-L1-targeted monoclonal antibodies
  • Uncontrolled diabetes mellitus
  • Severe or uncontrolled cardiovascular disease
  • Any other serious underlying medical, psychiatric, psychological, familial or geographical condition, which in the judgment of the investigator may interfere with the planned staging, treatment and follow-up, affect patient compliance or place the patient at high risk from treatment-related complications
  • Had an allogeneic tissue/solid organ transplant
  • Ongoing supplementation with OptiFibre® or another fiber supplement

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Treatment
  • Allocation: Randomized
  • Interventional Model: Parallel Assignment
  • Masking: None (Open Label)

Arms and Interventions

Participant Group / Arm

Participant Group / Arm

A group or subgroup of participants in a clinical trial that receives a specific intervention/treatment, or no intervention, according to the trial's protocol.
Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.
Experimental: High-fiber diet
Patients in this arm will receive a high-fiber diet over the period of 6 weeks.
Dietary supplement: High-fiber diet
Patients in the intervention arm will receive a high-fiber diet through daily consumption of a defined amount of plant-based fibers from a commercial product.
No Intervention: No high-fiber diet
Patients in this arm will not receive an intervention and serve as control.

What is the study measuring?

Primary Outcome Measures

Primary Outcome Measures

In a clinical study's protocol, the planned outcome measure that is the most important for evaluating the effect of an intervention/treatment. Most clinical studies have one primary outcome measure, but some have more than one.
Outcome Measure
Measure Description
Time Frame
ctDNA clearance
Time Frame: 6 weeks
Fraction of patients achieving complete ctDNA clearance at 6 weeks
6 weeks

Secondary Outcome Measures

Secondary Outcome Measures

In a clinical study's protocol, a planned outcome measure that is not as important as the primary outcome measure for evaluating the effect of an intervention but is still of interest. Most clinical studies have more than one secondary outcome measure.
Outcome Measure
Measure Description
Time Frame
ctDNA dynamics
Time Frame: 3 and 6 weeks
ctDNA dynamics over 6 weeks
3 and 6 weeks
Radiological treatment response
Time Frame: 6 weeks and 6 months
Objective radiological response (RECIST 1.1)
6 weeks and 6 months
Disease control rate
Time Frame: 6 months
6-months disease control rate (non-progressive disease at 6 months)
6 months
Microbiota dynamics
Time Frame: 6 weeks
Gut microbiota dynamics by shotgun metagenomics
6 weeks
Systemic immune response
Time Frame: 6 months
Systemic immune response dynamics by high-dimensional flow cytometry
6 months

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Sponsor

The organization or person who initiates the study and who has authority and control over the study.
Cantonal Hospital of St. Gallen

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

Helpful Links

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

Study Start

The actual date on which the first participant was enrolled in a clinical study. The "anticipated" study start date is the date that the researchers think will be the study start date.
October 7, 2025

Primary Completion (Estimated)

Primary Completion

The date on which the last participant in a clinical study was examined or received an intervention to collect final data for the primary outcome measure. Whether the clinical study ended according to the protocol or was terminated does not affect this date. For clinical studies with more than one primary outcome measure with different completion dates, this term refers to the date on which data collection is completed for all the primary outcome measures. The "anticipated" primary completion date is the date that the researchers think will be the primary completion date for the study.
December 31, 2027

Study Completion (Estimated)

Study Completion

The date on which the last participant in a clinical study was examined or received an intervention/treatment to collect final data for the primary outcome measures, secondary outcome measures, and adverse events (that is, the last participant's last visit). The "anticipated" study completion date is the date that the researchers think will be the study completion date.
December 31, 2027

Study Registration Dates

First Submitted

First Submitted

The date on which the study sponsor or investigator first submitted a study record to ClinicalTrials.gov. There is typically a delay of a few days between the first submitted date and the record's availability on ClinicalTrials.gov (the first posted date).
March 16, 2026

First Submitted That Met QC Criteria

First Submitted That Met QC Criteria

The date on which the study sponsor or investigator first submits a study record that is consistent with National Library of Medicine (NLM) quality control (QC) review criteria. The sponsor or investigator may need to revise and submit a study record one or more times before NLM's QC review criteria are met. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
March 16, 2026

First Posted (Actual)

First Posted

The date on which the study record was first available on ClinicalTrials.gov after National Library of Medicine (NLM) quality control (QC) review has concluded. There is typically a delay of a few days between the date the study sponsor or investigator submitted the study record and the first posted date.
March 19, 2026

Study Record Updates

Last Update Posted (Actual)

Last Update Posted

The most recent date on which changes to a study record were made available on ClinicalTrials.gov. There may be a delay between when the changes were submitted to ClinicalTrials.gov by the study's sponsor or investigator (the last update submitted date) and the last update posted date.
March 19, 2026

Last Update Submitted That Met QC Criteria

Last Update Submitted That Met QC Criteria

The most recent date on which the study sponsor or investigator submitted changes to a study record that are consistent with National Library of Medicine (NLM) quality control (QC) review criteria. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
March 16, 2026

Last Verified

Last Verified

The most recent date on which the study sponsor or investigator confirmed the information about a clinical study on ClinicalTrials.gov as accurate and current. If a study with a recruitment status of recruiting; not yet recruiting; or active, not recruiting has not been confirmed within the past 2 years, the study's recruitment status is shown as unknown.
October 1, 2025

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

Other Study ID Numbers

Identifiers or ID numbers other than the NCT number that are assigned to a clinical study by the study's sponsor, funders, or others. These numbers may include unique identifiers from other trial registries and National Institutes of Health grant numbers.
  • BASEC2025-00650
  • KFS-6039-02-2024 (Other Grant/Funding Number: Krebsforschung Schweiz)
  • Lungenliga Ost (Other Grant/Funding Number: Lungenliga Ost)
  • Swiss Cancer Foundation (Other Grant/Funding Number: Swiss Cancer Foundation)
  • Nestlé Health Science (Other Grant/Funding Number: Nestlé Health Science)

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

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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