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 2024 ASCO Annual Meeting.

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.