The microbiome has been implicated in several cancers including gastrointestinal and breast cancer with many hypotheses proposed as to why bacterial dysbiosis is associated with cancer onset. Recent studies in mice as well as epidemiological studies have provided further evidence that specific bacterial composition led to tumor formation and this could be blocked by antibiotics. In a new study, scientists at the University of Pennsylvania aimed to use epidemiological data to evaluate the association between antibiotics and cancer risk of the skin, lung, breast, gastrointestinal and genitourinary tract.
The scientists used data from The Health Improvement Network (THIN) database, a medical record database from the United Kingdom containing the information of approximately 11 million individuals. They looked at 15 different malignancies and in order to focus on sporadic cancers, they excluded any individuals with family cancer syndromes as well as any subjects that were diagnosed prior to the age of 20. With every case of cancer, they used four matched controls resulting in 125, 441 cases and 490, 510 controls analyzed for the study.
They found that the use of penicillin resulted in an increased risk of esophageal, gastric, and pancreatic cancers and was 1.4 for gastric cancers associated with greater than 5 courses of antibiotics. Lung cancer risk also increased with penicillin, cephalosporins, or macrolides. Prostate cancer also so a slight increase with several types of antibiotics as well as breast cancer after sulphonamide exposure.
They found for any type of malignancy there was no association between a single course of antibiotic use and increased risk but there was a correlation between greater number of antibiotic courses and cancer risk. Penicillin was associated with the most significant cancer risk while anti-virals, anti-fungals, and tetracylines were not associated with increased risk of cancer. While the increase in incidence was quite small (approximately 20:100,000), it is an important finding that antibiotics may be having a wider impact than previously believe. It is important that future studies look at the mechanisms for how antibiotics are causing this increased cancer risk as well as the effects of age of antibiotic exposure on cancer risk.