Scientists now believe that overuse of antibiotics could be contributing to the increasing incidence of colorectal cancer (affecting both the colon and rectum). Drawing on a large primary care database of up to two million people in Scotland, researchers from the University of Aberdeen and Queen’s University Belfast looked at health records of nearly 8,000 people with colorectal cancer (sometimes referred to as bowel cancer). Their results, published in July 2021 in the Annals of Oncology, showed that antibiotic use was linked with an increased risk of colon cancer across all ages. But the likelihood was almost 50 percent higher in those under age 50, compared with 9 percent higher in individuals over 50. “Junk food, sugary drinks, obesity, and alcohol are likely to have played a part in that rise [of colorectal cancer cases], but our data stress the importance of avoiding unnecessary antibiotics, especially in children and young adults,” said lead author Sarah Perrott, MBChB, of the School of Medicine at the University of Aberdeen, in a July 2 statement. Dr. Perrott and her colleagues noted that antibiotic use was linked to cancers in the first part of the colon (the right side) in the under-50 group. Quinolones and sulfonamides combined with trimethoprim, which are used to treat a wide range of infections, were connected with these right-side cancers. Elena A. Ivanina, DO, MPH, director of neurogastroenterology and motility at Lenox Hill Hospital in New York City, who was not involved in the study, commented that it was too early to say if excessive use of antibiotics could be a causative factor. “This observational study from Europe is not the first study to look at the increased risk of colorectal cancer after antibiotic use, but reinforces a fascinating connection between the microbiome and cancer,” said Dr. Ivanina. “The findings are especially relevant as they discovered that oral antibiotic use was associated with increased colon cancer in people under 50, a population that has been seeing increased rates of colon cancer with no clear explanation. Considering the widespread use of unnecessary antibiotics, this would be a perfect target for cancer prevention if this association is held up in future prospective studies that clarify causation.” Next, researchers said they want to explore whether antibiotic use causes changes in the microbiome, which might make the colon more susceptible to cancer.
