Oral Antibiotic Use and Risk of Colorectal Cancer in the UK

Colorectal cancer incidence in the US, and quite similarly in other western societies, has experienced rapid changes over the last few decades. Thus, a steady increase until the mid-1980s was followed by a constant decline afterwards, only explained in part by the progressive generalization of colorectal cancer screening. A more recent trend has been a notable surge in incidence among younger individuals, which has averaged a 1.8% annual increase from 2006 to 2015 among those younger than 55 years of age. These rapid changes can only be explained by evolving environmental exposures and lifestyle factors. Among those, the last century has seen the development and subsequent generalization of the use of antibiotics. The use of these has been clearly linked with a disruption in gut microbiota, and this disruption has been associated with several gastrointestinal diseases such as colorectal cancer. In fact, several studies have suggested a direct relationship between antibiotic use and colorectal cancer development.

In this context, Zhang et al aimed to determine the effects of different families of antibiotics on colorectal cancer incidence by location. In order to do so, the authors used the rich, population-based, prospective database from the British Clinical Practice Research Datalink, which includes 14 million patients with antibiotic prescription data and variables such as BMI, alcohol and tobacco consumption, and comorbidities. The results showed a complex picture with a dose-dependent increased risk of colon cancer, particularly in the proximal colon, among antibiotic users. The greatest association was seen in individuals who took anti-anaerobic antibiotics. On the other hand, the effect was the opposite for rectal cancers, with the most significant reduction in risk among individuals who took tetracyclines. Understanding the mechanisms of these effects and how we can leverage those to tackle this cancer is a new challenge we face now.