Table 1.

Summary of studies on the role of antibiotics in colon and rectal cancers.

Type of Antibiotics	Study Type	Major Finding	Reference
Penicillin	Human, retrospective	Exposure to multiple courses of penicillin increases colon cancer risk	[34]
Overall antibiotics	Human, retrospective	Exposure to antibiotics increases the relative risk for primary colon cancer	[47]
Oral use of ampicillin/amoxicillin	Human, retrospective	Oral use of ampicillin/amoxicillin increased the risk of colon cancer	[35]
Oral use of tetracyclines	Human, retrospective	Oral use of tetracyclines reduced the risk of rectal cancer	[35]
Oral administration of the mix of antibiotics: ampicillin/neomycin/ metronidazole/ vancomycin	Animal study, azoxymethane (AOM)/dextran sodium sulfate (DSS)-induced model of colitis-associated cancer (CAC)	Pretreatment of animals with the mix of antibiotics 3 weeks prior, but not during AOM/DSS treatment, did not decrease tumorigenesis	[48]
Oral or intravenous medication of one of the seven antibiotic classes, including penicillins, cephalosporins, macrolides, tetracyclines, sulfonamides, quinolones, and nitroimidazoles	Human, retrospective	Antibiotic exposure could be during therapy with bevacizumab inversely associated with the mortality in metastatic colorectal cancer	[49]