Circulating tumor DNA (ctDNA) as a new predictive and prognostic marker in colorectal tumors

In the last 20 years, oncogenetic research has focused on personalizing anticancer treatment and identifying
driver mutations, i.e. implementing targeted tumor therapy in the everyday practice. In parallel, there is a growing need to monitor therapeutic efficacy and more accurately estimate prognosis in order to determine which patients will benefit most from the planned treatment.

By examining circulating tumor DNA (ctDNA) using liquid biopsies, we can not only identify predictive biomarkers,
but robust clinical data also support the prognostic value of these tests. The level of plasma ctDNA is highly dependent on tumor burden and tumor cell turnover, which, since the half-life of ctDNA in plasma is very short, can be imaged in almost real time using liquid biopsy. Thus, the sensitivity and specificity of plasma ctDNA assays are particularly high in the detection of molecular residual disease (MRD). The essence of MRD analysis is to search for the presence of a small amount of residual tumor in the body that is not macroscopically detectable after curative anticancer treatment, using ctDNA testing. The presence of MRD is significantly associated with unfavorable disease-free survival.

Currently, several clinical trials are underway in colorectal tumors to include ctDNA-based MRD assessment in the
adjuvant therapeutic decision-making process, as part of risk stratification. In our current review, in addition to presenting the available ctDNA assay methods, we focus on these new results – we review the potential possibilities of ctDNA-guided adjuvant care and therapy escalation or de-escalation.