Postoperative changes in plasma miR21‐5p as a novel biomarker for colorectal cancer recurrence: A prospective study

Cancer‐related microRNAs (miRNAs) are emerging as promising and noninvasive biomarkers for colorectal cancer (CRC). This study aimed to investigate the usefulness of postoperative changes in plasma miR21‐5p levels for recurrence and progressive disease (PD) after surgical resection. This study was a prospective study of 103 CRC patients who underwent surgical resection. Self‐paired plasma samples collected pre‐operation (Pre), 7 days post‐operation (POD7), 1 month post‐operation (POM1), and 6 months post‐operation (POM6) were analyzed. The miRNA levels were evaluated by quantitative reverse transcription PCR. Among the enrolled patients, ten cases (9.7%) of postoperative recurrence and six cases (5.8%) of postoperative PD occurred at POM6. In the recurrence and PD group, plasma miR21‐5p levels significantly increased (POM1: P < .01, POM6: P < .01, respectively). The area under the curve (AUC) value for postoperative changes in plasma miR21‐5p levels at POM1 and POM6 to discriminate recurrence and PD were 0.675 and 0.715, respectively. Combined analysis with postoperative carcinoembryonic antigen (CEA) level in discriminating recurrence and PD increased AUC values (POM1: 0.715 and POM6: 0.789). Furthermore, multivariate analysis for recurrence and PD after surgical resection showed that postoperative changes in the plasma miR21‐5p level at POM1 and POM6 were independent prognostic factors (POM1: P = .03, POM6: P < .01). The postoperative changes in plasma miR21‐5p level could be a useful noninvasive biomarker for monitoring and predicting recurrence and PD after surgical resection of CRC patients. Furthermore, plasma miR21‐5p can predict recurrence and PD after surgical resection.