Dr Chao on the Correlation Between Broad-Spectrum Antibiotics and 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 rationale for investigating the association between the use of broad-spectrum antibiotics and the risk of developing early-onset colorectal cancer (CRC). Notably, these data were presented at the 

Chao begins by saying that investigators are keenly interested in exploring hypotheses that may help explain the increasing trend of early-onset CRC, which is defined as CRC that occurs in patients younger than 50 years of age. This form of CRC has seen a rising incidence since the 1990s in the United States and several other developed countries, according to Chao. Understanding the factors contributing to this rise is crucial, as the prevalence of the risk factors responsible for this increase must have also shown an upward trend preceding the rise in CRC cases because it takes several years for CRC to become clinically evident, Chao adds.

One factor investigators addressed in this study was the role of broad-spectrum antibiotics. The number of prescriptions for these antibiotics has increased significantly over the decades—from few in the 1950s to tens of millions in 2002, she continues. Although overall antibiotic use has plateaued since 2000, the use of broad-spectrum antibiotics has continued to rise, Chao states, noting that this trend aligns with the increasing incidence of early-onset CRC.

The potential mechanism by which broad-spectrum antibiotics might contribute to CRC involves their impact on gut microbiota, she expands. Broad-spectrum antibiotics can significantly alter the gut microbiome, which may influence cancer development, Chao says. Given this possible mechanism and the observed trends in antibiotic use, investigators believe that broad-spectrum antibiotics could be a contributing factor to the rise in early-onset CRC. Understanding the role of antibiotics in the development of CRC could provide valuable insights into the prevention and management of this disease, Chao concludes.

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Chun Chao, PhD, MS, discusses the association between the use of broad-spectrum antibiotics and the risk of developing early-onset colorectal cancer.

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 

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.

Chun Chao, MS, PhD, discusses the impact of broad-spectrum antibiotic use on the risk of developing early-onset colorectal adenocarcinoma.

Chun Chao, PhD, MS

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Dr Chao on the Correlation Between Broad-Spectrum Antibiotics and Early-Onset CRC

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