Liquid biopsy for detection of EGFR T790M mutation in nonsmall cell lung cancer: An experience of proficiency testing in Taiwan

Background: The use of liquid biopsy to detect epidermal growth factor receptor (EGFR) T790M mutation in nonsmall cell lung cancer (NSCLC) is a promising method to screen patients eligible for third-generation EGFR inhibitors. Proficiency testing (PT) programs involving liquid biopsy are currently lacking. In this study, we conducted a PT program to assess the quality assurance of liquid biopsy tests for detecting EGFR T790M mutation in molecular pathology laboratories in Taiwan. Methods: Whole blood samples (2 mL) with various concentrations of the EGFR T790M mutation were prepared and analyzed in six participating laboratories using their clinically validated assays. Results: For circulating cell-free DNA (cfDNA) isolation, three of the six participating laboratories used the cobas cfDNA Sample Preparation Kit, and three used the QIAamp Circulating Nucleic Acid Kit. For testing platforms, two of the six participating laboratories used mass spectrometry, three used the cobas EGFR mutation test, and one used a laboratory-developed test. There was 100% concordance in detection of all the given concentrations of EGFR T790M mutation between the participating laboratories and different testing platforms. The testing platforms used by all participating laboratories could successfully detect EGFR T790M mutation to an expected frequency of 1%. Conclusion: In this first PT program using liquid biopsy in Taiwan, local clinical laboratories were suitably equipped and proficient in the use of cfDNA to test for the EGFR T790M mutation. Establishing a routine PT system to ensure the reliability and accuracy of liquid biopsy in clinical practice in Taiwan would be helpful.