Study findings presented by Perrott et al at the ESMO World Congress on Gastrointestinal Cancer (Abstract SO-25) showed that the use of antibiotics may be linked to colon tumor formation across all patient age groups, especially in those younger than 50 years. These results raise fresh concerns about the impact of the estimated 65% increase in global antibiotic consumption reported between 2000 and 2015, despite not showing a direct cause and effect.
“To our knowledge, this is the first study to link antibiotic use with the growing risk of early-onset colon cancer—a disease that has been increasing at a rate of at least 3% per year over the past 2 decades. Junk food, sugary drinks, obesity, and alcohol [consumption] are likely to have played a part in that rise, but our data stress the importance of avoiding unnecessary antibiotics, especially in children and young adults,” said presenting author Sarah Perrott, of the University of Aberdeen.
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Methodology and Results
Using a large Scottish primary care database, the study looked at nearly 8,000 people with colorectal cancer matched with healthy controls.
Researchers found antibiotic use was associated with an increased risk of colon cancer across all ages, but the risk was increased by almost 50% in patients younger than age 50 compared to 9% in those older than 50. In the younger age group, antibiotic use was linked to cancers in the first part of the colon (the right side). Quinolones and sulfonamides/trimethoprim, which are used to treat a wide range of infections, were associated with these right-side cancers.
Senior study author Leslie Samuel, MB ChB, of the Aberdeen Royal Infirmary, explained that the contents of the right side of the colon are more liquid and that the natural bacteria living there, called the microbiome, may be different from further along the colon.
“We now want to find out if there is a link between antibiotic use and changes in the microbiome that can make the colon more susceptible to cancer, especially in younger people. It’s a complex situation, as we know that the microbiome can quickly revert to its previous state even when the bowel has been cleared 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,” said Dr. Samuel.
Commenting on the new research, Alberto Sobrero, MD, of Ospedale San Martino, Genoa, Italy, explained that of the 2 million people diagnosed with colorectal cancer worldwide each year, younger people aged 20 to 40 years generally have a worse prognosis than older patients, because they are often diagnosed later.
“Physicians are less likely to investigate a patient with abdominal discomfort for colon cancer if they are in their 30s than if they are in their 70s…As a result, their cancer is usually diagnosed at a later stage, when it is more difficult to treat,” he said.
Alberto Sobrero, MD
Dr. Sobrero believes that physicians should now consider colorectal cancer as a possible diagnosis in younger patients experiencing abdominal symptoms, and he supports more research into the multiple possible causes of the rising incidence of the disease in this age group.
“It is too early to say if excessive use of antibiotics could be a causative factor, and we need to understand more about the possible role of the microbiome in colorectal cancer before we consider the impact of antibiotics on the intestinal flora. However, the new research does remind us that antibiotics should not be given unless they are really needed, and we cannot exclude the possibility that unnecessary use of antibiotics may be exposing people to an increased risk of cancer,” Dr. Sobrero concluded.
Disclosure: For full disclosures of the study authors, visit annalsofoncology.org.The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.