Researchers at the Johns Hopkins Kimmel Cancer Center conclude that taking even a single course of antibiotics might boost–albeit slightly the risk of developing colon cancer but not rectal cancer a decade later. The findings, reported in the August 20 issue of the journal Gut ; highlight the need for judicious use of this broad category of drugs; which are frequently improperly or overprescribed, the report authors say.

Risk of developing colon cancer

The primary message of this study is the importance of antibiotic stewardship: not treating common viral infections with antibiotics; using them for the shortest time period possible, and using targeted antibiotics rather than broad spectrum ones.  This research adds to our understanding that these drugs can have significant off-target effects; including the induction of chronic illnesses.” Study leader Cynthia L. Sears, M.D., Bloomberg~Kimmel Professor of Cancer Immunotherapy at the Johns Hopkins Kimmel Cancer Center Sears cautions that medical records studies like hers are not designed to demonstrate cause and effect; but to identify possible associations between risk factors and disease.

But she notes that because the database held so much specific information over a long period of time that the study authors concluded that the most likely explanation for the bump in colon cancer risk is the radical change that antibiotics wreak on the microbiome the collection of bacteria that live in the intestines. Therefore Antibiotics are widely prescribed throughout the world to treat bacterial infections, and there is growing evidence; including several epidemiological database studies; that link use of these drugs to the risk of colorectal cancer; explains Sears and Jiajia Zhang, M.D., M.P.H., a Bloomberg~Kimmel Institute for Cancer Immunotherapy researcher.

Largest electronic medical

However, the investigators say, these past studies have had a variety of drawbacks, including failure to control for other colorectal cancer risk factors (family history, history of obesity, smoking, alcohol use, and diabetes) recall bias in patients’ recollections about antibiotic use; failure to separate data about colon and rectal cancers; and too few study participants to produce meaningful conclusions.

To learn more about the association between antibiotics and colorectal cancers, Sears, Zhang, and their colleagues mined data from the Clinical Practice Research Datalink (CPRD); one of the world’s largest electronic medical record databases of “anonymized” clinical records, information that does not identify individual patients. CPRD holds information on more than 11 million patients in the U.K., including data on drug prescribing and diagnoses; making this study the first population-based study to examine the association of antibiotic exposure and risk of colorectal cancer.