J. Carter1, U. Netz1, K. Feagins1, V. States1, M. R. Eichenberger1, S. Galandiuk1 1University Of Louisville,Department Of Surgery,Louisville, KY, USA
Introduction:
Recurrence following treatment for colorectal cancer is common. Current blood-based tests, such as serum carcinoembryonic antigen (CEA), are used both for post-operative surveillance and for monitoring response to therapy. CEA; however, lacks sufficient sensitivity and specificity to accurately detect recurrence of CRC or its precursor lesion, advanced adenoma (CAA). microRNAs (miRNAs) have been associated with both the diagnosis and regulation of different disease processes. They are short, non-coding RNAs that play an important role in gene expression. We believe miRNAs may have a potential role in monitoring therapy following removal of an adenoma or cancer. We have previously identified longitudinal changes in plasma miRNA in patients with CAA and CRC. Our aim is to confirm significantly dysregulated miRNAs identified from screening studies in plasma samples obtained from patients with CAA and CRC prior to and after endoscopic or surgical removal.
Methods:
Plasma was isolated from 24 patients, 12 with CAA (>0.6cm diameter) and 12 with stage II-III CRC prior to treatment and 4-6 weeks following endoscopic removal or surgical resection. Total RNA was extracted and RNA quality and quantity were assessed. Reverse transcription and quantitative real-time polymerase chain reaction was performed using specific primers and probes for the miRNAs of interest. A total of 11 miRNAs were included for assessment: 4 miRNAs identified from our screening cohort to be significantly dysregulated between pre-treatment and post-removal samples and 7 miRNAs that were significantly different between CAA and controls and CRC and controls in a prior study. Data was analyzed comparing pre-treatment samples to post-removal samples using paired t-tests after normalizing raw cycle threshold data to endogenous RNU6 and miR-16.
Results:
Of the 11 analyzed miRNAs, miR-29c (sensitivity 50% 95% CI:25-75, specificity 83% 95% CI:54-97%, AUC 0.67 95% CI:0.45-0.90) was found to be downregulated in pre-treatment plasma samples compared to post-removal samples in CRC (p<0.05 at α=0.05). miR-374a (sensitivity 50% 95% CI:25-75, specificity 83% 95% CI:54-97%, AUC 0.66 95% CI:0.43-0.89) was found to be downregulated in pre-treatment plasma samples compared to post-removal samples in CAA (p<0.05 at α=0.05).
Conclusion:
The expression levels of miR-29c and miR-374a, were different in pre-treatment as compared to post-removal plasma samples in patients with CRC and CAA, respectively. These findings may help provide for a relatively non-invasive method of monitoring therapy or assessing response to treatment. Future considerations should include standardized protocols for assessing miRNA pre- and post-neoadjuvant therapy in patients with rectal cancer in order to determine the effect of such treatment on tumor regression.