Approximately 20% of locoregional colorectal carcinoma (CRC) relapse after standard of care treatment. Therefore, it is necessary to personalize our adjuvant strategies and define this subgroup, which remains at high risk after treatment. Circulating tumour DNA (ctDNA) is cell-free DNA from apoptotic cancer cells, which carries the whole genome information of the primary tumour and has emerged as good candidate to guide our therapy decisions in the future. It was shown that high levels of ctDNA after adjuvant chemotherapy is a poor prognostic factor. Moreover, it was presented at ESMO 2019 in Barcelona that patients with advanced colorectal carcinomas and ctDNA-positive samples after surgery had a significantly decreased 2‑year disease-free survival in comparison to ctDNA-negative patients. That means, ctDNA could be a tool to select this high-risk subgroup in advanced CRC in order to prolong or intensify adjuvant chemotherapy and to avoid insufficient treatment.