Unnecessary Use of Antibiotics May Lead to Early Onset CRC in Patients Under 50 Years

Unnecessary antibiotic use may lead to an increased risk of colon cancer in patients under the age of 50, according to a first-of-its-kind study presented at the 2021 World Congress on Gastrointestinal Cancer.1

“To our knowledge, this is the first study linking antibiotic use to the growing risk of early-onset colon cancer — a disease that has increased by at least 3% per year over the past two decades,” says Sarah Perrot. , School of Medicine, Medical Sciences and Nutrition, University of Aberdeen, United Kingdom, in a statement ahead of the presentation. “Junk foods, sugary drinks, obesity and alcohol have likely played a role in that increase, but our data emphasize the importance of avoiding unnecessary antibiotics, especially in children and young adults.”

Between 2000 and 2015, antibiotic consumption worldwide increased by 65%, although no clear causality was demonstrated.² The number of colon cancer cases in people under 50 has also increased significantly.

In the study, researchers examined the relationship between antibiotic exposure and early colorectal cancer (EO-CRC) risk for people under age 50, and evaluated antibiotic use in older adults age 50 or older with CRC for comparison.

Using a Scottish primary care database of up to 2 million people, the study looked at nearly 8,000 patients (n = 7,903) with colon cancer (bowel cancer and rectum) equivalent to 30,418 people without colon cancer. Of those with colon cancer, 5,281 had colon cancer, 2,622 rectally, and 445 were under the age of 50.

In both age groups, antibiotic use was associated with an increased risk of colorectal cancer, especially in the EO-CRC cohort (adjusted odds ratio [aOR], 1.49; 95% CI, 1.07-2.07; P = 0.018) versus in the cohort older than 50 years (aOR 1.09; 95% CI 1.01-1.18; P = 0.029). In the younger cohort, antibiotic use was associated with cancers of the right side of the colon.

According to one of the authors of the study, Leslie Samuel, MD, of the Department of Clinical Oncology, Aberdeen Royal Infirmary in the United Kingdom, the contents of the right side of the colon are more fluid and thus the microbiome may differ from other areas of the colon. the large intestine.

“We now want to know if there is a link between antibiotic use and changes in the microbiome that may make the colon more susceptible to cancer, especially in younger people,” Samuel said in a statement. “It’s a complex situation because we know that the microbiome can quickly return to its previous state, even if the gut has been emptied for a diagnostic procedure such as an endoscopy. We don’t yet know whether antibiotics can have effects on the microbiome that are direct or indirect.” can contribute to the development of colon cancer.”

Significantly, antibiotic use was associated with an increased risk of proximal colon cancer (pCC) in patients under 50 (aOR, 3.78; 95% CI, 1.60-8.92; P = 0.002), but not among the older age group (aOR, 0.89; 95% CI, 0.72-1.11; P = .315), which was considered statistically significant (P = .001). Of both age groups, most antibiotic classes were not significantly associated with colon, rectal, or distal colon cancer; however, quinolones (aOR, 7.47; 95% CI, 1.40-39.94; P = .019) and sulfonamides/trimethoprim (aOR, 4.66; 95% CI, 1.66-13.09; P = .003) were associated with pCC in the EO – CRC cohort only.

Rectal cancer was not associated with antibiotic use in either stratum except for non-anti-anerobic antibodies in the EO-CRC cohort (aOR 1.70; 95% CI 1.06-2.74; P = 0.029).

“Doctors are less likely to examine a patient with abdominal discomfort for colon cancer in their 30s than in their 70s, and younger patients are not eligible for colon cancer screening,” Alberto Sobrero, Ospedale professor San Martino, Genoa, Italy, noted. “As a result, their cancer is usually diagnosed at a later stage, when it’s more difficult to treat.”

“Our findings suggest that antibiotics may play a role in colon tumor formation in all age groups, especially those in those” [under] 50,” the study authors concluded. “It is possible that exposure to antibiotics could contribute to the observed increase in EO-CRC, particularly in the proximal colon. If confirmed, our study will provide further research to reduce, where possible, the frequent and unnecessary prescription of antibiotics.” Reduce.”


Perrot S, McDowell R, Murchie P, Cardwell C, Samuel L. Global rise in early colorectal cancer: a link with antibiotic use? Ann Oncol. 2021;32(suppl 3):SO-25.Klein EY, Van Boeckel TP, Martinez EM, et al. Global increase and geographic convergence in antibiotic use between 2000 and 2015. Proc Natl Acad Sci VS A. 2018;15(15) :E3463-E3470. doi:10.1073/pnas.1717295115

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