Table 1.

ctDNA applications for detection and genotyping of CRC.

Reference	Findings
Frattini et al., 2005	DNA levels in plasma are significantly higher in CRC patients, they decrease during their follow‐up and increase again at tumor recurrence.
Flamini et al., 2006	ctDNA, especially when used in combination with CEA, represents a potentially useful tool for the diagnosis of early‐stage colorectal cancer.
Umetani et al., 2006	Since ctDNA integrity may reflect cancer cell death, the length of its fragments might also be used as a marker for tumor detection.
Spindler et al., 2015	Tumor‐specific KRAS mutations in plasma have prognostic value.
Genotyping cancer alleles in ctDNA of CRC patients
Mouliere et al., 2013 Siravegna et al., 2015 Thierry et al., 2014a Thierry et al., 2014b	Assessment of hotspot alterations in RAS and BRAF genes in CRC patients.
Reinert et al., 2015	Post‐surgery surveillance: ctDNA levels are quantified using droplet digital PCR and correlated to clinical findings.
Tie et al., 2015	Tumor burden evaluation and prediction response to standard chemotherapy in early stage CRC patients.
Bettegowda et al., 2014	KRAS mutant fragments are detected in the blood of patients with KRAS‐mutant colorectal tumors, with high specificity (99.2%) and sensitivity (87.2%). KRAS mutant levels also correlate with a shorter overall survival.
Monitoring drug resistance and clonal evolution in the blood of cancer patients
Diaz et al., 2012 Misale et al., 2012	RAS pathway mutations associated to acquired resistance to EGFR‐specific antibodies can be detected in the blood of colorectal cancer patients before disease progression is clinically manifest.
Siravegna et al., 2015	ctDNA in blood‐based liquid biopsies is used to track clonal evolution and targeted drug responses in CRC patients. The proportion of KRAS‐mutated alleles dynamically increased and decreased in the presence and absence of the anti EGFR drug.
Mohan et al., 2014	Whole genome sequencing of plasma of CRC patients treated with anti‐EGFR therapy unveils several copy number changes, including loss of the APC chromosomal 5q22 region and amplifications in known gene involved in the resistance to EGFR blockade such as MET, ERBB2 and KRAS.