Antibiotics Associated With Increased Risk of Colon Cancer Among Certain Patients


New research presented at the ESMO World Congress on Gastrointestinal Cancer suggests the use of antibiotics may increase the risk of colon cancer, especially in individuals under age 50 years. The investigators warn that the unnecessary use of antibiotics could potentially put patients at risk.

The study utilized a Scottish primary care database to examine close to 8000 patients with bowel cancer matched with individuals without bowel cancer. Through this analysis, the investigators found that the use of antibiotics was associated with an increased risk of colon cancer across all age groups. Further, the risk increased by almost 50% for patients under age 50 years, while the increase was only 9% in those aged over 50 years.

“To our knowledge, this is the first study to link antibiotic use with the growing risk of early onset colon cancer—a disease which has been increasing at a rate of at least 3% per year over the last 2 decades,” said Sarah Perrott, from the University of Aberdeen, in a data presentation. “Junk food, sugary drinks, obesity, and alcohol are likely to have played a part in that rise, but our data stress the importance of avoiding unnecessary antibiotics, especially in children and young adults.”

The investigators found that antibiotics were linked to cancers in the first part of the colon, the right side, and in the younger patients. Specifically, the development of these right-side cancers was associated with quinolones and sulfonamides/trimethoprim, which are used to treat a number of infections. According to the investigators, the contents of the right side of the colon are more liquid, and as such, the microbiome in this section of the colon may be different from those in other areas of the colon.

“We now want to find out if there is a link between antibiotic use and changes in the microbiome, which can make the colon more susceptible to cancer especially in younger people,” said Leslie Samuel, MSc, in a press release. “It's a complex situation as we know that the microbiome can quickly revert to its previous state even when the bowel has been cleared out for a diagnostic procedure such as an endoscopy. We don't yet know if antibiotics can induce any effects on the microbiome that could directly or indirectly contribute to development of colon cancer.”

Further compounding the cause for concern, younger patients with colon cancer—between the ages of 20 and 40 years—tend to have a worse prognosis than older individuals, as they are often diagnosed later.

“Physicians are less likely to investigate a patient with abdominal discomfort for colon cancer if they are in their 30s than if they are in their 70s, and younger patients are not eligible for bowel cancer screening,” said Alberto Sobrero, MD, in the release. “As a result, their cancer is usually diagnosed at a later stage, when it is more difficult to treat.”


Bowel cancer data reinforce need to reduce unnecessary antibiotic use [news release]. EurekAlert; July 2, 2021. Accessed July 6, 2021.

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