Table 1.

Definitions of key terms

Key term	Definition
ARE	Gastrointestinal symptoms that occur within 12 weeks of abdominopelvic radiotherapy in cancer patients, including nausea, vomiting, diarrhea and abdominal pain, etc. Featured by progressive cell impairment and inflammation, the rapidly renewing intestinal epithelium is the major target and thus symptoms are reversible and short-lasting
CRE	Gastrointestinal symptoms that occur after 12 weeks until years after abdominopelvic radiotherapy in cancer patients, including dysmotility, malabsorption, strictures, perforation and bleeding, etc. Featured by mucosal atrophy, vascular sclerosis and progressive fibrosis, the slowly renewing intestinal parenchymal wall is involved, and thus symptoms are usually irreversible
Gut microbiota	Microorganisms habituating in the gastrointestinal tract of host, including bacteria, archaea, fungi and viruses, with broad impacts on metabolism and pathophysiology of host
MT	The transfer of microbial content from a healthy donor into the gastrointestinal tract of a diseased recipient, and can be classified into faecal MT, oral MT, selective MT according to the sources
Probiotic	Live microorganisms that, when consumed in adequate amounts, beneficially affect the host by direct bacterial-host interactions or derived metabolites
Prebiotic	Nondigestible ingredients e.g., fibers, that reach the colon and promote growth of specific colonic bacteria to beneficially improve host health
Synbiotic	Combination of probiotics and prebiotics and are believed to be more efficient in conferring health benefits

ARE Acute radiation enteropathy, CRE Chronic radiation enteropathy, MT Microbiota transplantation