NIH Research Festival
Background: The fecal microbiota has been observed to be associated with colorectal cancer (CRC) in case-control studies while some common oral microbes detected in fecal samples (e.g., Fusobacterium and Porphyromonas) have been associated with CRC. However, no studies have prospectively evaluated the association between oral microbiota and CRC risk. Methods: We conducted a nested case-cohort study within the Prostate, Lung, Colorectal, and Ovarian Cancer (PLCO) screening trial using pre-diagnostic oral wash specimens. We included 470 prospectively ascertained CRC cases and a referent subcohort of 1,218 PLCO participants. DNA was extracted using the QIAsymphony and the V4 region of the 16S rRNA gene was sequenced using the MiSeq. Bioinformatics were performed using QIIME2. Odds ratios (OR) and 95% confidence intervals (95% CI) were calculated using logistic regression with adjustment for age, sex, and smoking. Results: Alpha diversity, such as the Shannon Index, was not associated with CRC (OR 1.10; 95% CI: 0.93, 1.30); similarly, no associations were detected with measures of beta diversity. The presence of Fusobacterium was non-significantly inversely associated with CRC (OR 0.60; 95% CI: 0.28, 1.26) while the presence of Porphyromonas was not associated with CRC (OR 1.04; 95% CI: 0.75, 1.45). Conclusions: In this large, prospective cohort, the oral microbiota was not associated with CRC risk. The dysbiosis in feces at the time of CRC diagnosis may occur later in the carcinogenesis process or may only be detectable in feces. Additional studies are needed to evaluate the temporal association between the microbiota and CRC risk.
Scientific Focus Area: Epidemiology
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