Dr Chao on the Association Between Broad-Spectrum Antibiotic Use and the Risk of Early-Onset CRC

Chun Chao, PhD, MS, research scientist III, Division of Epidemiologic Research, Kaiser Permanente; professor, Department of Health Systems Science,a cancer epidemiologist and researcher at Kaiser Permanente Bernard J Tyson School of Medicine, discusses the association betweenimpact of broad-spectrum antibiotic use on and the risk of developing early-onset colorectal adenocarcinomacancer (CRC), as presented at the 2024 ASCO Annual Meeting.

The Chao and colleagues conducted a nested, case control study, conducted within the Kaiser Permanente Southern California (KPSC) health system to assess, aimed to evaluateassessed whether the use of broad-spectrum antibiotics is associated with an increased risk of developing early-onset colorectal cancer (eoCRC).disease.

Notably, the study included patients between aged 15 to -49 years of age who were diagnosed with invasive colorectal adenocarcinoma between 2009 and 2021. The control group was matched at a 10:1 ratio based on age, sex, and length of KPSC membership.

Findings from the study showed Chao begins by noting that the overall use of broad-spectrum antibiotics was not associated with a significant increase in early-onset eoCRC risk, with an odds ratio (OR) of 1.15 (95% CI,: 0.88-1.49), Chao reports.

However, when evaluating the cumulative duration of antibiotic use, an interesting pattern emerged, Chao notes. For patients with more than three 3 months of cumulative broad-spectrum antibiotic use, the OR for developing early-onset eoCRC was 1.59 (95% CI,: 0.95-2.65). Chao explains that although , suggesting a potential increased risk, althought this OR was not statistically significant, . Chao emphasizes that the lower confidence interval was close to one1, indicating a possible association between long-term antibiotic use and increased risk of early-onset CRC.

The study also examined the association between broad-spectrum antibiotic use and colon adenocarcinoma specifically. For individuals with more than 1one month of cumulative antibiotic use, the OR was 1.50 (95% CI,: 0.99-2.27)), highlighting a near-significant increased risk. Chao notes that no significant associations were found for antibiotic use within 5-10 or 2-5 years prior to diagnosis.

Chao concludes that the findingsOverall, these findings suggest a possible association between longer-term cumulative use of broad-spectrum antibiotics and increased risk of early-onset colorectal adenocarcinoma. The study underscores the importance of considering the etiologic window when assessing antibiotic exposure, Chao emphasizes. Chao calls concludes by calling for larger studies with long-term follow-up to confirm these findings and better understand the relationship between antibiotic use and colorectal cancer CRC risk.