Tie J, Cohen JD, Wang Y, et al. - Researchers investigated whether serial postsurgical and postchemotherapy circulating tumor DNA (ctDNA) analysis could provide a real-time indication of adjuvant therapy efficacy in stage III colon cancer. In this multicenter, Australian, population-based cohort biomarker study, 96 patients with stage III colon cancer provided serial plasma samples after surgery and after chemotherapy. Individual patients’ tumors were assessed for somatic mutations via massively parallel sequencing of 15 genes commonly mutated in colorectal cancer. ctDNA was quantified using personalized assays. Outcomes revealed that a 3-year recurrence-free interval differ significantly between patients with detectable vs undetectable levels of circulating tumor DNA after surgery (47% vs 76%) and after completion of chemotherapy (30% vs 77%). This suggests the possible utility of postsurgical and postchemotherapy circulating tumor DNA analyses for recognizing patients at high risk of recurrence despite completing standard adjuvant treatment, offering a unique opportunity to examine additional therapeutic approaches.