Antibiotic Use and Colorectal Cancer in Olmsted County, Minnesota

To evaluate the association between antibiotic use and colorectal cancer (CRC) risk using US population-based data from the Rochester Epidemiology Project (REP), and to assess potential effect modification by tumor site, age group, and antibiotic class through prespecified subgroup analyses.

We conducted a retrospective case-control study using REP data from Olmsted County, Minnesota. Cases of CRC diagnosed between January 1, 2010, and December 31, 2020, were matched to up to four controls by age, sex, and residence. Antibiotic prescriptions from January 1, 2005, until 2 years before CRC diagnosis/index date were categorized by cumulative exposure: none, 1-15 (low), 16-60 (intermediate), or greater than 60 days (high). Conditional logistic regression estimated odds ratios (ORs) and 95% CIs, adjusting for comorbidities, smoking, and alcohol abuse. Subgroup analyses were stratified by age, tumor site, and antibiotic class.

Among 2454 participants (512 cases, 1942 controls), no statistically significant association was found between antibiotic use and CRC risk across all exposure durations compared with no antibiotic use. Adjusted ORs were 0.92 (95% CI, 0.69 to 1.23) for low, 0.91 (95% CI, 0.68 to 1.23) for intermediate, and 1.06 (95% CI, 0.77 to 1.46) for high exposure. Subgroup analyses showed no significant associations by tumor location or antibiotic class. However, in individuals younger than 65 years of age, low and intermediate exposure were associated with significantly reduced CRC ORs (0.56 and 0.62, respectively).

Antibiotic exposure was not associated with increased CRC risk overall. Observed inverse associations in younger adults highlight the need for further research in larger, more diverse populations.