Detection of KRAS Mutations Using Extracellular Vesicle DNA in Colorectal Cancer Patients

Abstract

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.