Immunotherapy is a major therapeutic approach in oncology, and emerging evidence links the composition and function of the gut microbiota to immunotherapy effectiveness. Dietary components that alter the intestinal microbiome, notably dietary fiber, have been proposed as modulators of immune responses during cancer treatment. This scoping review synthesized clinical evidence on the impact of dietary fiber intake on immunological responses and outcomes in patients undergoing cancer immunotherapy.
The review aimed to evaluate published clinical evidence concerning the relationship between dietary fiber intake, immune modulation, and response to immunotherapy in patients with cancer. The scope included studies that assessed habitual diet, dietary interventions, or fiber supplementation and reported associations with immune markers, microbiota changes, or clinical outcomes.
The authors performed an integrative scoping search of MEDLINE, BVS, and EMBASE databases. Search descriptors included "Neoplasms," "Dietary Fiber," and "Immunomodulation." Inclusion criteria were original clinical studies involving patients with cancer who were receiving immunotherapy and in which dietary fiber intake was evaluated either through habitual diet assessment, dietary interventions, or supplementation. Eligible studies also needed to report associations between dietary fiber and at least one of: immune response, gut microbiota composition or function, or clinical outcomes related to immunotherapy.
A total of 325 records were identified through the search. After screening and applying the predefined inclusion criteria, three studies met the eligibility requirements and were included in the review. The abstract does not provide detailed study-level methods such as study designs, sample sizes, or duration; those specifics were not reported in the source abstract.
From 325 records screened, three original clinical studies were included. All included studies involved patients with melanoma who received immune checkpoint inhibitors, predominantly anti-PD-1 therapies. Across these studies, higher dietary fiber intake correlated with improved therapeutic responses to immunotherapy. The studies also reported favorable changes in the gut microbiota associated with higher fiber intake.
The review highlights a consistent association in the included melanoma cohorts between greater fiber consumption and better immunotherapy outcomes, along with microbiome signatures that were considered beneficial. Precise quantitative results, measures of effect size, and statistical analyses from the individual studies are not provided in the abstract available from the source.
The findings summarized in this scoping review support the hypothesis that dietary fiber contributes to modulation of the gut microbiota, which in turn may influence the immunological response to cancer immunotherapy. The included clinical studies centered on melanoma patients treated with immune checkpoint inhibitors, mostly anti-PD-1 agents, and reported links between higher fiber intake, microbiome alterations, and superior therapeutic responses.
Mechanistic rationale referenced in the review and in related literature (as cited in the article) includes the role of fiber fermentation products such as short-chain fatty acids in regulating immune cell function and promoting anti-tumor immunity via gut-immune axis pathways. The review cites prior influential reports that have explored how diet and probiotics can influence melanoma immunotherapy response, placing the included clinical observations in the context of growing translational and mechanistic evidence.
However, the scoping review also underscores the limited clinical evidence base: only three eligible clinical studies were identified among 325 records. The abstract does not provide study-level detail such as randomized designs, comparator arms, fiber dosages, timing relative to immunotherapy, or confounding control. Because these methodological details are not reported in the abstract, conclusions about causality, optimal fiber sources or amounts, and generalizability beyond melanoma cannot be drawn from the information in the source.
This scoping review concludes that dietary fiber is relevant for modulating the gut microbiota and may enhance the effectiveness of immunotherapy in cancer patients. The included clinical evidence—limited to three studies involving melanoma patients receiving predominantly anti-PD-1 therapy—reported associations between higher fiber intake, favorable microbiome changes, and improved therapeutic responses. The review highlights potential clinical importance but also indicates that the available clinical literature is sparse; further detailed and controlled clinical studies are needed to define specific recommendations.
The scoping review is published in Cancer Medicine (2026 Aug;15[8]:e72108). It is indexed with PMID 42533258 and DOI 10.1002/cam4.72108. The article is available as a free publication according to the source abstract.
cancer; dietary fiber; gut microbiota; immune response; immunotherapy