Validation of Cell-Free DNA Collection Tubes for Determination of EGFR Mutation Status in Liquid Biopsy from NSCLC Patients

Introduction Precision medicine has revolutionized the understanding and treatment of cancer by identifying subsets of patients who are amenable to specific treatments according to their molecular characteristics, as exemplified by epidermal growth factor receptor (EGFR) mutations in non-small cell lung cancer (NSCLC). Although tissue biopsy is the gold standard for determining molecular alterations in tumors, its limitations have prompted the development of new techniques for studying tumor biomarkers in liquid biopsies, such as mutation analysis in cell-free DNA (cfDNA). cfDNA analysis can accurately determine tumor progression and prognosis and more effectively identify appropriate targeted therapies. However, cfDNA is vulnerable, particularly during plasma sample shipping. Objective We compared the cell- and DNA-stabilizing properties of cell-free DNA blood collection tubes (BCTs) with those of the traditional shipping method (frozen plasma) for EGFR mutation testing using the cobas (R) EGFR Mutation Test v2 in a prospective cohort of 49 patients from three different Spanish hospitals. Methods In total, 98 NSCLC samples, two from each patient, were studied; five of the 49 cases were considered invalid by cobas (R) with one of the two shipping methods analyzed. After excluding these samples, we analyzed 88 samples from 44 patients. Considering the current methodology (frozen plasma) for sending samples as the gold standard, we evaluated the sensitivity and specificity of cfDNA BCT shipment. Results The global agreement between the two methods was 95.4%, with 100% sensitivity and 94.6% specificity for the cfDNA BCTs. cfDNA BCTs had a positive predictive value of 81.8% and negative predictive value of 100%. Conclusion cfDNA BCTs have the same sensitivity for EGFR mutation analysis in liquid biopsy as the current methodology and very high specificity. They also have some additional advantages in terms of collection and further shipment. Therefore, cfDNA BCTs can be perfectly incorporated into the routine practice for EGFR mutation determination. Funding Roche Farma S.A., Spain.