Background and study aim: Colorectal cancer (CRC) is a major cause of cancer-related deaths in both men and women. Colonoscopy is the most reliable tool for CRC diagnosis, but its complexity and costs hamper its wide application. There is a pressing need for new non-invasive biomarkers to improve early diagnosis of CRC. Aim was to assess serum micro RNA (miR) -21and miR-92a for diagnosis of CRC.
Patients and Methods: This comparative cross sectional study was carried out on 50 subjects. The cases group comprised 35 consecutive treatment naive patients with sporadic CRC proved by colonoscopy and histopathology of the biopsied specimens as well as abdominal CT which all together helped in tumor staging applying TNM, Duke's and MAC Coller stages. Serum carcinoembryonic antigen (CEA) and cancer antigen (CA) 19-9 were also assessed. Fifteen matched healthy subjects (with normal colonoscopy) served as the control group.
Results: Serum levels of miR-21 and miR-92a were significantly higher (P<0.001) in cases compared to the control (5.53 ± 0.17≠4.82 ± 0.20 and 7.01 ± 0.234 ≠ 6.56 ± 0.20 log RU, respectively). Serum miR-21 and miR-92a levels revealed a significantpositive relation with tumor size and TNM and MAC Coller stages (P<0.05). No significant relationship was detected between either serum miR-21 or miR-92a levels with age or sex. Applying ROC curve, at a cutoff value of ≥5.25 log RU, serum miR-21 was 94.3% sensitive and 93.3% specific for detection of CRC with an AUC= 0.99 and serum miR-92a level  at a cut off  value ≥6.75 log RU,  was 91.4% sensitive and 80% specific for detection of CRC with AUC= 0.91. When both markers were combined, the sensitivity and specificity were 97.1% and 93.3% respectively.
Conclusion: Serum miR-21 and miR-92a levels represent a sensitive and specific tool for CRC diagnosis, with higher accuracy of miR-21.