Functional convergence amid taxonomic variability in gut microbiome-immune checkpoint inhibitor research: a bibliometric and mechanistic synthesis.

Immune checkpoint inhibitors (ICIs) have transformed cancer therapy, yet clinical responses remain highly variable, and microbiome-associated findings lack reproducibility across studies. Increasing evidence implicates the gut microbiome in modulating ICI efficacy; however, findings remain inconsistent at the taxonomic level, raising the possibility that functionally convergent immunological mechanisms may underlie this apparent variability. To address this, a critical synthesis was conducted, integrating bibliometric mapping of publications indexed in the Web of Science Core Collection (2013-2025; n = 2,195) with a secondary analysis of ClinicalTrials.gov to evaluate interventional activity. Bibliometric approaches assessed scientific production, thematic evolution, and co-citation structure, complemented by a cross-cohort functional integration of representative clinical and preclinical studies to evaluate whether microbiome-ICI interactions converge on shared immunological pathways despite divergent taxonomic signatures. Publication output increased steadily, with a marked translational surge following landmark clinical studies in 2018 and a peak in trial initiation in 2021. Thematic analyses revealed a shift from mechanistic and tumor-centered research toward clinically oriented and intervention-driven themes, including microbiome modulation, microbial metabolites, and the tumor microenvironment. Although individual response-associated taxa differed substantially across independent cohorts, qualitative functional integration supported a model of convergence in immunomodulatory pathways involving short-chain fatty acid production, dendritic cell activation, and CD8+ T-cell priming. Collectively, these findings suggest that apparent taxonomic inconsistencies across microbiome-ICI studies may reflect underlying functional convergence rather than biological contradiction, supporting a shift toward function-based frameworks for biomarker discovery and microbiome-directed immunomodulation.