RRM2 and colorectal cancer: Significance of RRM2 gene expression for prognosis of colorectal cancer patients was further corroborated in the validation set I, where patients with intratumoral RRM2 transcript level higher than median had significantly longer DFI compared to patients with levels below the median (n = 66, P = 0.009, did not pass the correction for multiple testing, Fig. 2a, the rest of results in Additional file 1: Figure S2).