Profiling small RNAs in CRC screening samples such as the widely used fecal immunochemical test, is it possible?

Faecal microRNAs represent promising molecules with potential clinical interest as non-invasive diagnostic and prognostic biomarkers for their stability and detectability. Colorectal cancer (CRC) screening based on the fecal immunochemical test (FIT) is an effective tool for prevention of cancer development. However, due to the poor sensitivity of FIT for premalignant lesions, there is a need for implementation of complementary tests. Improving the identification of individuals who would benefit from further investigation with colonoscopy using molecular analysis, such as miRNA profiling of the FIT leftover buffer, would be ideal due to its widespread use. In the present study, we applied small RNA sequencing to FIT leftover samples collected from two European screening populations. We showed robust detection of miRNA and microbial profiles, which were similar to those obtained from specimens sampled using RNA stabilising buffers and archived fecal samples. Detected miRNAs exhibited differential abundance between CRC and control samples that was consistent between sampling methods, suggesting a promising potential to identify small RNA CRC biomarkers using FIT leftovers. We demonstrated that it is possible to analyse gut miRNAs in FIT leftover samples and envision that these potential biomarkers can complement the FIT in large scale screening settings.