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

Chun Chao, PhD, MS, cancer epidemiologist, Kaiser Permanente Southern California Department of Research & Evaluation; professor, Kaiser Permanente Bernard J Tyson School of Medicine, discusses the association between broad-spectrum antibiotic use and the risk of developing early-onset colorectal cancer (CRC), as presented at the 2024 ASCO Annual Meeting.

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

Notably, the study included patients between 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 that the overall use of broad-spectrum antibiotics was not associated with a significant increase in early-onset CRC 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 3 months of cumulative broad-spectrum antibiotic use, the OR for developing early-onset CRC was 1.59 (95% CI, 0.95-2.65). Chao explains that although this OR was not statistically significant, the lower confidence interval was close to 1, 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 1 month of cumulative antibiotic use, the OR was 1.50 (95% CI, 0.99-2.27). Chao notes that no significant associations were found for antibiotic use within 5-10 or 2-5 years prior to diagnosis.

Overall, these findings underscore the importance of considering the etiologic window when assessing antibiotic exposure, Chao emphasizes. Chao concludes by calling for larger studies with long-term follow-up to confirm these findings and better understand the relationship between antibiotic use and CRC risk.