This case-control study from the UK utilized 28,980 colorectal cancer cases and 137,077 matched controls. Antibiotic exposure was identified through a prospective nationwide database. The adjusted odds ratios (ORs) for colon cancer showed excess and dose-dependent risk, with ORs of 1.08, 1.14, 1.15, and 1.17 for exposures of 1 to 15, 16 to 30, 31 to 60, and >60 days, respectively. The effects were greater in the proximal colon, and antibiotics effective against anaerobic bacteria were especially associated with proximal colon cancer risk. On the other hand, antibiotics, particularly tetracycline, were protective against rectal cancer.
This large study suggests changes in colonic bacterial flora induced by antibiotic use can affect colorectal cancer risk. Thus, as we hear so often, antibiotics should be used only when clearly needed.
Zhang J, Haines C, Watson AJM, et al. Oral antibiotic use and risk of colorectal cancer in the United Kingdom, 1989-2012: a matched case-control study. Gut
2019 Aug 19. (Epub ahead of print) (http://dx.doi.org/10.1136/gutjnl-2019-318593