Screening for colorectal cancer (CRC) is effective in average-risk population. The most extended strategy in organized programs involves the fecal immunochemical test, which is limited by low sensitivity for detection of advanced adenomas (AAs). We aimed to identify microRNA (miRNA) signatures in fecal samples that identify patients with AAs or CRC and might be used in non-invasive screening.

Our study comprised 4 stages. In the discovery phase, we performed genome-wide miRNA expression profiling of 124 fresh, paired colorectal tumor and non-tumor samples (30 colorectal tumors; 32 AAs) from patients in Spain. In the technical validation stage, miRNAs with altered expression levels in tumor vs non-tumor tissues were quantified by reverse transcription PCR in fecal samples from a subset of patients included in the discovery phase (n=39) and individuals without colorectal neoplasms (controls, n=39). In the clinical validation stage, the miRNAs found to be most significantly up-regulated by quantitative reverse transcription PCR analysis were measured in an independent set of fecal samples (n=767) from patients with positive results from fecal immunochemical tests in a CRC screening program. Finally, we developed model to identify patients with advanced neoplasms (CRCs or AAs) based on their miRNA profiles, using findings from colonoscopy as the reference standard.

Among 200 and 324 miRNAs significantly deregulated in CRC and AA tissues, respectively, 7 and 5 of these miRNAs were also found to be deregulated in feces (technical validation). Of them, MIR421, MIR130b-3p, and MIR27a-3p were confirmed to be upregulated in fecal samples from patients with advanced neoplasms. In our model, the combination of fecal level of MIR421, MIR27a-3p, and hemoglobin identified patients with CRC with an area under the curve (AUC) of 0.93, compared to an AUC of 0.67 for fecal hemoglobin concentration alone. The combination of markers identified patients with AA with an AUC value of 0.64, compared to an AUC of 0.59 for fecal hemoglobin concentration alone.

We found that imore accurately than fecal hemoglobin concentration alone. Assays for these miRNAs might be added to fecal tests for detection of CRC or AAs.