Redefining high-risk patients with stage II colon cancer by risk index and microRNA-21: results from a population-based cohort.

BACKGROUND: The aim of the present study was to analyse the prognostic value of microRNA-21 (miRNA-21) in patients with stage II colon cancer aiming at a risk index for this group of patients. METHODS: A population-based cohort of 554 patients was included. MicroRNA-21 was analysed by qPCR based on tumour tissue. An index was created using the coefficients obtained from a collective multiple Cox regression. The entire procedure was cross-validated (10-fold). The performance of the index was quantified by time-dependent receiver operating characteristics curves. RESULTS: High miRNA-21 expression was associated with an unfavourable recurrence-free cancer-specific survival (RF-CSS), hazard ratio 1.35 (95% confidence interval, 1.03-1.76) (P=0.028). The generated RF-CSS index divided the traditional high-risk patients into subgroups with 5-year RF-CSS rates of 87% and 73%, respectively (P<0.001). The overall survival (OS) index identified three different subgroups (P<0.001). Cross-validated 5-year OS rates were 88%, 68%, and 50%, respectively. CONCLUSIONS: This population-based study supports miRNA-21 as an additional prognostic biomarker in patients with stage II colon cancer. Furthermore, the introduction of a risk index may guide the use of postoperative adjuvant treatment in a more appropriate way compared with current practice.