Long-Term Antibiotic Use May Lead to Increased Risk of Cancer

Heavy antibiotic use at certain stages of life could cause conditions associated with cancer, later on.

According to a study published in Gut, an official journal of the British Society of Gastroenterology, young and “middle-aged” adults who were prescribed long-term regimens of antibiotics later had an increased risk of colorectal adenoma, a suspected precursor to cancer.

Andrew Chan, MD, a physician with the Clinical and Translational Epidemiology Unit at Massachusetts General Hospital in Boston and a co-author on the study, observed in an interview, “This study provides additional evidence that the body’s normal intestinal bacteria may play a role in maintaining health... disrupting the normal bowel bacteria may be harmful and have some long-term health outcomes including the possibility of developing colon polyps.” He added that his team’s findings indicate that physicians and patients should be “cautious” about disrupting normal bowel bacteria, which could occur when extended regimens of antibiotics are prescribed.

The group evaluated the association between antibiotics and colorectal adenoma by reviewing antibiotic use in a group of 121,700 US female patients, who are also nurses, participating in an ongoing study. The patients were between 30 and 55 years of age at enrollment in 1976, and have answered questions about their health every two years since the baseline of enrollment, when they provided a medical history. For this study, Dr. Chan and his team excluded all patients diagnosed with cancers other than non-melanoma skin cancer and those who had been diagnosed with colorectal polyps before 2004.

During the evaluation, the group discovered that 1,195 of 16,642 women presently aged 60 or older had had at least one colonoscopy between 2004 and 2010 and had newly-diagnosed adenomas. The women had otherwise similar histories to their counterparts without adenomas, but had antibiotic usage histories that involved long-term use while between the ages of 20 and ok39. “Compared to non-users, women who used antibiotics for two or more months during age 20 to 39 had a multivariable OR for adenoma of 1.36,” the group reported.

Similar results were reported for long-term use of antibiotics in those between the ages of 40 and 59. “Recent antibiotic use did not appear associated with colorectal adenoma,” Dr. Chan pointed out. His team noted, “Among women who had colonoscopy between 2008 and 2010, antibiotic use in the past four years was not associated with risk of adenoma.”

Although the group emphasized that their findings needed to be confirmed by other studies, they warned that the study “suggests the potential need to limit the use of antibiotics and sources of inflammation that may drive tumor formation.” CDC Safe Healthcare Blog contributor, and Director of the Human Microbiome Program at NYU, Martin Blaser, MD, agrees. “Fewer infections require an antibiotic than you might think,” he writes, adding, “When you look closer at the bacteria that live in our body, you will see that they play an intimate and crucial role in our growth, development, and maintenance of health….There is a growing body of research showing an association between early-life exposures to antibiotics and chronic diseases such as asthma, diabetes, and obesity.”