Utility of micro-ribonucleic acid profile for predicting recurrence of rectal cancer

In early-stage rectal cancer, the surgeon must decide between the high morbidity of radical surgery and the high recurrence rates of local excision. A prognostic marker could improve patient selection and lower recurrence rates. Micro-ribonucleic acids (miRNAs), small RNAs that often inhibit tumor suppressors, have shown prognostic potential in colorectal cancer. We hypothesized that high miRNA levels in malignant tissue from early-stage rectal cancer patients could predict recurrence after local excision.

We identified 17 early-stage rectal cancer patients treated with local excision between 1990 and 2005, four of whom had recurrences. Total RNA was extracted from benign and malignant tissue and used in quantitative real-time reverse transcriptase polymerase chain reaction to probe for miR-20a, miR-21, miR-106a, miR-181b, and miR-203. MiRNA data were evaluated for association with recurrence using univariate analysis with Wilcoxon rank sum test.

Malignant tissue in both patients who had recurrences and patients who did not have recurrences had equivalently high levels of miRNA. However, the benign tissue of patients who recurred contained significantly higher levels of all five miRNAs when compared with the benign tissue of nonrecurrent patients despite having no histological differences.

This is the first study to show that high miRNA levels of histologically benign tissue obtained from the surgical margin of locally excised rectal cancers can predict recurrence. The malignant miRNA levels did not have predictive value. Further investigation of miRNAs is needed to explore their potential for a more accurate prognosis of rectal cancer.