By Joseph E. Scherger, MD, MPH

Core Faculty, Eisenhower Health Family Medicine, Residency Program, Eisenhower Health Center, La Quinta, CA; Clinical Professor, Keck School of Medicine, University of Southern California, Los Angeles

SYNOPSIS: Swedish researchers saw an association between frequent antibiotic use and proximal colorectal cancer.

SOURCE: Lu SSM, Mohammed Z, Häggström C, et al. Antibiotic use and subsequent risk of colon cancer: A Swedish nationwide population-based study. J Natl Cancer Inst 2021; Sep 1:djab125. doi: 10.1093/jnci/djab125. [Online ahead of print].

A nationwide, population-based study in Sweden was conducted with a matched, case-controlled design. Data were collected from national registers where information was gathered from 2005 to 2016. The authors studied 40,545 cases of colorectal cancer with 202,720 controls, noting frequent antibiotic use was associated with a higher risk of proximal colon cancer (odds ratio, 1.17; 95% confidence interval, 1.05-1.31). The most common offending antibiotics were quinolones and sulfonamides with or without trimethoprim. There was an inverse association with rectal cancer in women.

Other investigators have found a relationship between antibiotic use and colorectal cancer.1,2 The composition and function of the gut microbiome are believed to play a role in colorectal cancer development.3,4 Antibiotics disrupt the gut microbiome and may result in dysbiosis, hindering the anti-inflammatory effects of some bacteria and producing more pathogenic bacteria.


Clinicians have come to better understand the risks of antibiotics and the importance of the gut microbiome. The rise in colorectal cancer cases among younger adults has led to calls to start screening patients at a younger age. Consider why this is happening. Dietary factors certainly play a role, especially consuming processed carbohydrates and meat. The potential role of antibiotics in causing colorectal cancer is poorly recognized. Association is not causation, but this study and other investigations raise concern. Anytime clinicians use antibiotics, especially repeatedly, consider the risk-benefit ratio and realize these drugs can cause harm. Diverticulitis is one example of a common inflammatory condition that may not require antibiotics in uncomplicated cases.5,6


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  3. Louis P, Hold GL, Flint HJ. The gut microbiota, bacterial metabolites and colorectal cancer. Nat Rev Microbiol 2014;12:661-672.
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  5. Jackson JD, Hammond T. Systematic review: Outpatient management of acute uncomplicated diverticulitis. Int J Colorectal Dis 2014;29:775-781.
  6. Shabanzadeh DM, Wille-Jørgensen P. Antibiotics for uncomplicated diverticulitis. Cochrane Database Syst Rev 2012;11:CD009092.