Microbiome-Host-Cancer Interface: A Narrative Review of Therapeutic Strategies, Current Challenges, and Global Opportunities

Background and Objective: The human microbiome is critical in carcinogenesis and treatment outcomes. Here, we discuss microbiome-host interactions, synthesise clinical evidence on targeted interventions, and consider challenges in translation. It examines cost-effective, scalable microbiome strategies to advance oncology care in low- and middle-income countries (LMICs) with emphasis on biomarker discovery and standardisation of research. Materials and Methods: We performed a narrative search of PubMed, Scopus, and Web of Science to identify peer-reviewed studies published from January 2010 through April 2026. The screening was focused on cancer-microbiome host interactions, mechanisms, efficacy, safety, and applicability for global health. For this review, a total of 150 eligible studies, including preclinical models, observational studies and clinical trials, were critically analysed. Results: The microbiome controls carcinogenesis through genotoxicity (e.g., colibactin from pks+ E. coli), chronic inflammation, T-cell priming and bioactive metabolites. In the clinic, faecal microbiota transplantation (FMT) and synbiotics improve anti-PD-1/PD-L1 response in refractory melanoma and reduce chemotherapy-induced mucositis and diarrhoea. Nevertheless, significant translational challenges include significant inter-individual heterogeneity, inconsistent strain engraftment, risk of opportunistic infection in immunocompromised patients and fractured regulatory frameworks. Conclusion: Microbiome intervention improves efficacy and reduces toxicity of cancer therapies. In settings with limited resources, inexpensive prebiotics and probiotics can be easily added to oncology care. Prioritisation is needed for global clinical translation of biomarker discovery, standardisation of research protocols, and inclusion of LMIC populations in trials.