Antibiotics may increase the risk of colon cancer, especially in younger people, U.K. researchers report.
"To our knowledge, this is the first study to link antibiotic use with the growing risk of early-onset colon cancer -- a disease which has been increasing at a rate of at least 3% per year over the last two decades," said study co-author Sarah Perrott, a cancer researcher at the University of Aberdeen.
The researchers' comparison of data from nearly 8,000 people in Scotland with colon and rectal cancer to folks without the disease found an association between antibiotic use and an increased risk of colon cancer at all ages.
The study found significant age-related differences, however. Antibiotic use was linked with a nearly 50% higher risk of colon cancer in folks under age 50, and a 9% higher risk in older people.
In younger people, antibiotic use was linked to cancers in the colon's right side. Quinolones and sulfonamides/trimethoprim -- antibiotics used to treat a wide range of infections -- were associated with these cancers.
The study doesn't prove antibiotics cause these cancers, only that there appears to a link.
But the researchers said their findings add to concerns about the effects of an estimated 65% increase in worldwide antibiotic use between 2000 and 2015.
The findings were presented Friday at the ESMO World Congress on Gastrointestinal Cancer 2021, which was held online.
"Junk food, sugary drinks, obesity and alcohol are likely to have played a part in [the rise in colon cancer], but our data stress the importance of avoiding unnecessary antibiotics, especially in children and young adults," Perrott said in a meeting news release.
Senior author Dr. Leslie Samuel noted that the contents of the right side of the colon are more liquid and the natural bacteria living there, called the microbiome, may be different from bacteria that reside farther down the colon.
"We now want to find out if there is a link between antibiotic use and changes in the microbiome which can make the colon more susceptible to cancer, especially in younger people," he said in the release.
Samuel, a consultant oncologist at the Aberdeen Royal Infirmary, said it is a complex challenge. That's because the microbiome can quickly return to its previous state even when the colon is cleaned out for a diagnostic procedure such as an endoscopy.
"We don't yet know if antibiotics can induce any effects on the microbiome that could directly or indirectly contribute to development of colon cancer," Samuel said.
Research presented at meetings is typically considered preliminary until published in a peer-reviewed journal.
The U.S. National Cancer Institute has more on colon cancer.
SOURCE: European Society of Medical Oncology, news release, July 2, 2021