Detection of <i>KRAS</i> Mutations Using Extracellular Vesicle <scp>DNA</scp> in Colorectal Cancer Patients

Liquid biopsy using circulating tumor DNA (ctDNA) is useful for precision medicine and molecular-guided oncology; however, its sensitivity is insufficient. We focused on DNA in extracellular vesicles (evDNA) as a new target for liquid biopsy and investigated its sensitivity. This observational study included 334 Stage I-IV colorectal cancer patients. evDNAs and ctDNAs were extracted from plasma collected before surgery. KRAS mutation status was analyzed using droplet digital PCR. One hundred and forty-eight patients had KRAS mutations in tumor tissues, and 186 patients had no KRAS mutations. In Stage II (Stage II 37.8% vs. 13.3%, p = 0.015) or III (Stage III 43.1% vs. 13.6%, p = 0.001) patients, sensitivities to detect KRAS mutations using evDNA were higher than those using ctDNA. Surprisingly, evDNA identified KRAS mutations in 13.8% of patients who lacked them in tumor tissue samples. Among Stage III patients, those with higher concentrations of evDNA had significantly poorer relapse-free survival compared with those who had lower concentrations of evDNA (p = 0.043). The use of evDNA improved the identification rate of KRAS mutations. By using evDNA, KRAS mutations were identified in more than 10% of patients without KRAS mutations in their tumor tissues. The concentration of evDNA can be a prognostic factor for Stage III colorectal cancer patients.