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Long-term antibiotic use linked to increased risk for colorectal adenomas
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Researchers associated long-term use of antibiotics in early to mid-adulthood with an increased risk for colorectal adenomas in a recent study.
These findings support the potential role of the gut microbiome in the development of colorectal cancer, and suggest that antibiotic use should be limited to reduce the risk for CRC, Andrew T. Chan, MD, MPH, of the division of gastroenterology at Massachusetts General Hospital and Harvard Medical School, and colleagues concluded.
While antibiotic use has been linked to CRC risk, prior studies are limited by their short-term follow-up, and have not explored the link between antibiotics and colorectal adenomas.
Andrew T. Chan
Chan and colleagues therefore prospectively evaluated this association in 16,642 women aged 60 years or older in 2004 who were enrolled in the Nurses’ Health Study. They assessed antibiotic use in both early adulthood (ages 20-39 years) and middle adulthood (ages 40-59 years), and all patients underwent at least one colonoscopy through 2010 to determine the presence of colorectal adenoma.
Overall, 1,195 patients were diagnosed with a colorectal adenoma during the study period.
The investigators observed a significantly increased risk for colorectal adenoma associated with longer use of antibiotics in both early adulthood (P for trend = .002) and middle adulthood (P for trend = .001), but not with recent antibiotic use within the past 4 years.
Those who used antibiotics for at least 2 months in early adulthood were 36% more likely to be diagnosed with a colorectal adenoma compared with those who had not received antibiotics for any extended period at the same age (OR = 1.36; 95% CI, 1.03-1.79).
Further, those who used antibiotics for at least 2 months in middle adulthood were 69% more likely to be diagnosed with a colorectal adenoma compared with those who had not received antibiotics for any extended period at the same age (OR = 1.69; 95% CI, 1.24-2.31).
Those who received antibiotics for at least 15 days at any time between ages 20 and 59 had a 73% increased risk for colorectal adenoma compared with those who had not received antibiotics for any length of time during the same age range (OR = 1.73; 95% CI, 1.19-2.51).
The investigators observed similar associations for both low- and high-risk adenomas, but observed “modestly stronger” associations for proximal vs. distal adenomas.
While the researchers cannot draw conclusions about causality due to the study’s observational design, they concluded that “the proposed link between exposure to antibiotics and development of colorectal neoplasia is biologically plausible.”
They also acknowledged that lack of data on type of antibiotic, and the possibility that some adenomas may have been present before antibiotic exposure, are additional study limitations.
“Additional studies investigating the impact of antibiotic exposure with gut microbial composition and function, particularly in relation to the mechanisms underlying colorectal carcinogenesis, are warranted,” they wrote. – by Adam Leitenberger
Disclosures: Chan reports he previously served as a consultant for Bayer Healthcare, Pozen and Pfizer for work unrelated to this study.
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