Antibiotic Exposure Linked to Increased Risk of Early-Onset Colorectal Adenoma
Prior antibiotic use may be associated with an increased risk of early-onset colorectal adenoma (EOCRA), according to a large population-based study evaluating long-term exposure and colorectal neoplasia risk. The findings add to growing concern about microbiome disruption as a contributor to rising rates of early-onset colorectal cancer.
Investigators conducted a nested case-control study including 6,936 EOCRA cases and 16,900 matched controls from a US healthcare system. Participants were younger than 50 years and matched by demographic and clinical factors, including colonoscopy timing and healthcare access. Antibiotic exposure was defined as oral use at least two years prior to diagnosis.
Overall, antibiotic use was associated with a higher risk of EOCRA in both unadjusted and adjusted analyses. The authors reported that “oral antibiotic use was associated with an increased risk of EOCRA,” with an adjusted odds ratio of 1.45. Risk was observed across antibiotic classes, including both broad- and narrow-spectrum agents.
A dose-response relationship was identified. EOCRA risk increased with the number of antibiotic prescriptions, peaking among individuals with 7 to 9 dispensations. Timing also influenced risk, with the strongest association observed five to eight years after exposure. The authors noted that risk “increased steadily as the number of antibiotic dispensations increased” and was highest several years after use.
These findings support a potential role of microbiome disruption in colorectal carcinogenesis.
The authors concluded that their results “support the hypothesis that antibiotic exposure may influence development of early-onset colorectal neoplasia,” while emphasizing the essential role of antibiotics in clinical care.
Reference
Bal A, Mishra P, Zhong SK et al. Oral antibiotic use and risk of early-onset colorectal adenomas: a nested case-control study. Presented at: Digestive Disease Week; May 2–5, 2026; Chicago, Illinois.
