The Microbiome and Radiation Induced-Bowel Injury

Tomoko Kumagai, Farooq Rahman and Andrew M. Smith

Nutrients

One in three people will develop cancer at some point in their lives. Radiotherapy is used to treat approximately 50% of cancer patients. However, its toxic effect to the surrounding normal healthy tissue remains a major drawback. 

Radiation-induced bowel injury is an undesirable and often debilitating consequence of radiation therapy for cancer, and most commonly occurs with radiotherapy to the abdomen and pelvic region. Between 60 and 80% of patients develop early intestinal inflammation which recedes within a few months; however, a significant number develop ‘delayed’ bowel toxicity, characterised by chronic inflammation and ischaemia resulting in irreversible mucosal atrophy, intestinal fibrosis and microvascular sclerosis. Once established, this is a chronic progressive irreversible condition. 

The pathophysiology of radiation-induced bowel injury is poorly understood, although we now know that it derives from a complex interplay of epithelial injury and alterations in the enteric immune, nervous, and vascular systems in genetically predisposed individuals. Furthermore, evidence supporting a pivotal role for the gut microbiota in the development of radiation-induced bowel injury has been growing. 

In this review, we aim to appraise our current understanding of radiation-induced bowel injury and the role of the microbiome in its pathogenesis as well as prevention and treatment. Greater understanding of the relationship between the disease mechanism of radiation-induced bowel injury and gut microbiome might shed light on potential future prevention and treatment strategies through the modification of a patient’s gut microbiome.

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