Microbiome and Abdominopelvic Radiotherapy Related Chronic Enteritis: A Microbiome-based Mechanistic Role of Probiotics and Antibiotics.

Chronic diarrhea and abdominal pain after radiotherapy continue to be a problem in cancer survivors. Gut microbiomes are essential for preventing intestinal inflammation, maintaining intestinal integrity, maintaining enterohepatic circulation, regulating bile acid metabolism, and absorption of nutrients, including fat-soluble vitamins. Gut microbiome dysbiosis is expected to cause inflammation, bile acid malabsorption, malnutrition, and associated symptoms. Postradiotherapy, Firmicutes and Bacteroidetes phylum are significantly decreased while Fusobacteria and other unclassified bacteria are increased. Available evidence suggests harmful bacteria Veillonella, Erysipelotrichaceae, and Ruminococcus are sensitive to Metronidazole or Ciprofloxacin. Beneficial bacteria lactobacillus and Bifidobacterium are relatively resistant to metronidazole. We hypothesize and provide an evidence-based review that short-course targeted antibiotics followed by specific probiotics may lead to alleviation of radiation enteritis.