Fecal miR-106a is a useful marker for colorectal cancer patients with false-negative results in immunochemical fecal occult blood test.

BACKGROUND Immunochemical fecal occult blood test (iFOBT) is widely used for colorectal cancer screening; however, its sensitivity is insufficient. We recently reported a fecal microRNA (miRNA) test (FmiRT) to detect colorectal cancer. In this study, we investigated a new colorectal cancer screening method combining iFOBT and FmiRT to improve the sensitivity compared with iFOBT alone. METHODS In total, 117 colorectal cancer patients and 107 healthy volunteers were enrolled. Ten-milligram fecal samples were collected and iFOBT was conducted. Fecal RNA was extracted from residuum of iFOBT and then the expression of 14 kinds of miRNA was analyzed for the FmiRT using real-time reverse transcription PCR. RESULTS Levels of fecal miR-106a expression in iFOBT+ patients and iFOBT- patients were significantly higher than in healthy volunteers (P = 0.001). The sensitivity and specificity of FmiRT using miR-106a were 34.2% and 97.2%, and those of iFOBT were 60.7% and 98.1%, respectively. The overall sensitivity and specificity of the new screening method combining iFOBT and FmiRT were 70.9% and 96.3%, respectively. One quarter of colorectal cancer patients with false-negative iFOBT seemed to be true positive upon adding FmiRT using fecal miR-106a. CONCLUSIONS Fecal miR-106a is a good molecular marker to identify colorectal cancer patients from among those with negative iFOBT results. FmiRT combined with iFOBT may improve the sensitivity to detect colorectal cancer. IMPACT We have shown the usefulness of fecal miR-106a to detect the colorectal cancer patients among those with negative iFOBT results.