Clinical question: Is bacteremia from certain microbes associated with colorectal cancer?
Background: Streptococcus bovis bacteremia is classically associated with colorectal cancer. A number of other bacterial species have been found in colorectal cancer microbiota and may even exert oncogenic effects. However, it is not known whether bacteremia from these microbes is associated with colorectal cancer.
Study design: Retrospective cohort study.
Setting: Public hospitals in Hong Kong.
Synopsis: Using the Clinical Data Analysis and Reporting System (representing greater than 90% of inpatient services provided in Hong Kong), researchers identified 15,215 patients with bacteremia from 11 genera of bacteria known to be present in the colorectal cancer microbiota, including Bacteroides, Clostridium, Filifactor, Fusobacterium, Gemella, Granulicatella, Parvimonas, Peptostreptococcus, Prevotella, Solobacterium, and Streptococcus. Compared with matched controls without bacteremia, a higher proportion of exposed patients had a subsequent diagnosis of colorectal cancer (1.69% vs. 1.16%; hazard ratio, 1.72; 95% confidence interval, 1.40-2.12). Bacteremia with other organisms was not associated with colorectal cancer, and bacteremia with the preidentified organisms was not associated with other types of non–colorectal cancer or nonmalignant gastrointestinal diseases, with the exception of a few genera commonly associated with diverticulitis.
Given the observational nature of this study, no causal relationship can be established. It is not clear if these species are involved in the oncogenesis of colorectal cancer or if colorectal tumors merely serve as a site of entry for bacteria into the bloodstream.
Bottom line: Bacteremia with certain bacterial genera is associated with colon cancer and should prompt consideration of colonoscopy to evaluate for malignancy.
Citation: Kwong TNY et al. Association between bacteremia from specific microbes and subsequent diagnosis of colorectal cancer. Gastroenterology 2018 Aug;155(2):383-90.
Dr. Scarpato is clinical instructor in the division of hospital medicine, University of Colorado, Denver.