Ohta R, Yamada T, Sonoda H, et al. - The quantity of circulating tumor DNA (ctDNA) derived from urine (trans-renal ctDNA) was determined and the accuracy of KRAS mutation detection in relation to disease stage in colorectal cancer is examined. Researchers obtained urine, plasma, and tissue samples from consecutively resected colorectal cancer patients. Among 200 participating patients, tumor tissue from 84 patients (42.0%) had detection of KRAS mutations. They identified a significantly lower concentration of trans-renal ctDNA (trtDNA) relative to plasma. Findings suggested equal potential of trtDNA and ctDNA and indicated that combination analysis significantly improved the sensitivity.