Microbiome and Cancer Therapy

The human microbiome has emerged as a critical regulator of cancer initiation, progression, and therapeutic response, reshaping contemporary paradigms in oncology. Accumulating evidence demonstrates that microbial communities residing in the gut, tumor microenvironment, and other anatomical niches modulate host immunity, inflammation, metabolism, and drug efficacy. These interactions profoundly influence responses to conventional cancer treatments, including chemotherapy, radiotherapy, immunotherapy, and targeted therapies. Dysbiosis, characterized by altered microbial composition and function, has been associated with therapeutic resistance, increased toxicity, and poor clinical outcomes. This chapter provides a comprehensive overview of the role of the microbiome in cancer therapy, highlighting mechanistic insights into host–microbe–drug interactions. Key topics include microbiome-mediated modulation of anticancer drug metabolism, immune checkpoint inhibitor efficacy, and treatment-related adverse effects. Emerging microbiome-targeted therapeutic strategies such as probiotics, prebiotics, synbiotics, postbiotics, dietary interventions, antibiotic stewardship, and fecal microbiota transplantation (FMT) are critically discussed in the context of precision oncology. Additionally, advances in microbiome-based biomarkers, diagnostic tools, and personalized treatment approaches are explored. This chapter further addresses translational challenges, safety considerations, regulatory perspectives, and future directions for integrating microbiome modulation into cancer therapeutics. By bridging microbiology, immunology, pharmacology, and clinical oncology, this chapter aims to provide researchers and clinicians with a holistic understanding of how microbiome science can redefine cancer treatment strategies and improve therapeutic outcomes.