The Microbiota–Diet–Immunity Axis in Cancer Care: From Prevention to Treatment Modulation and Survivorship

Growing evidence highlights the pivotal role of the gut microbiota in cancer development, progression, response to therapy, and survivorship. Diet plays a central role in shaping gut microbiota composition, influencing the immune system and overall host health. Plant-based diets and the Mediterranean diet promote health-associated microbial communities that increase the production of several metabolic-end products, including short-chain fatty acids that support mucosal barrier integrity, anti-inflammatory effects, and modulation of the immunity of the host. Conversely, Western dietary patterns promote cancer progression and negatively impact the response to standard treatments. Furthermore, gut microbiota influences the effectiveness of cancer therapies, including chemotherapy, radiotherapy and, mainly, immunotherapy. Modulating microbial species, their metabolites, or their activities in the cancer microenvironment through dietary interventions, common or engineered probiotics, prebiotics, postbiotics, antibiotics or fecal microbial transplant are emerging as promising strategies for cancer prevention and tailored management in survivorship. In this review, we explore the intricate interplay between diet, gut microbiota, and cancer, focusing on how specific microbial communities’ impact therapeutic outcomes, and the challenges in the modulation of the microbiota environment through several interventions, including diet. This emerging paradigm paves the way for integrating nutrition and microbiota-targeted strategies as innovative tools in the context of precision medicine.