Colorectal Cancer

Increases in colorectal adenoma (the initial sage of colorectal cancer) are reported to be associated with long-term use of antibiotics. A study carried out to assess long-term and short-term use of antibiotics in relation to colorectal adenomas found that long-term antibiotic use in early/middle adulthood is associated with increased risk of colorectal adenoma.


In recent years, use of antibiotics has increased dramatically in the USA. Accumulating evidence suggests a correlation between antibiotic use and disorders such as obesity, celiac disease and colorectal cancer. These illnesses may have originated from imbalance of gut microflora following exposure to anti-bacterial medicines. A balanced microbial presence in gut is crucial for maintaining proper function. Antibiotics can cause shift microbial diversity, increasing prevalence of bacteria not targeted by a specific drug. This could destabilize the metabolic state and promote inflammation, a known risk for colorectal cancer. Previous studies have shown an association between antibiotics and colon cancer; however, it is not currently known if there is a link between antibiotic treatment and early adenoma, the first stage of colon cancer.

As it takes about a decade for colorectal cancer to develop, the evaluation of exposure to antibiotic treatment should come years later. In a 2017 study published in the BMJ Colon, researchers evaluated the appearance of colon adenoma in 16642 women (>60 years of age) following exposure to antibiotics at a younger age (20-39 and 40-59). Time periods of exposure to antibiotics analyzed were: no treatment, <15 days, 15 day-2 month and> 2 month. Data based on patient’s history of antibiotics use at younger age (questionnaires’ mailed every two years) and colonoscopy results was collected during 2004-2010.

A strong association between increased duration of antibiotic treatment and colon adenoma was reported for both age groups (20-39 and 40-59) with higher correlation – 1.69 (as compared to 1.36) for 40-59 age group. In contrast, recent antibiotic use didn’t appear to correlate with risk to adenoma.

The study results imply that use of antibiotics for long periods of time (>2 month) during early adulthood has a strong association with increased risk for colorectal adenoma after the age of 60. This observation is supported by study from Finland, which demonstrated that patients receiving more antibiotic prescriptions (6% compare to 1%) have a 15% higher risk of developing colon cancer during 9years of follow up.

Future studies should address route of antibiotic treatment as well as the association of specific antibiotics with risk for colon carcinoma, factors which were not addressed in this initial study. Altogether, the findings suggest that there is a need to limit antibiotic use, as preventive action to reduce cases of inflammation, a known risk factor for colorectal cancer.


Written By: Bella Groisman, PhD

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