Microdroplet digital PCR: detection and quantitation of biomarkers in archived tissue and serial plasma samples in patients with lung cancer.

INTRODUCTION: There is much interest in the use of noninvasive biomarkers in the management of lung cancer, particularly with respect to early diagnosis and monitoring the response to intervention. Cell-free tumor DNA in patients with cancer has been shown to hold potential as a noninvasive biomarker, in which the response to treatment may be evaluated using a blood test only. Multiple technologies have been suggested as being appropriate to measure cell-free tumor DNA. Microdroplet digital polymerase chain reaction (mdPCR) has a number of attributes that suggest it may be a useful tool for detecting clinically relevant genetic events. It offers precise and accurate quantitation of mutant alleles, including rare variants. METHODS: We evaluate the performance of mdPCR in the analysis of DNA extracted from reference standards, tumor biopsies, and patient plasma. RESULTS: The potential of mdPCR to detect clinically relevant mutations is demonstrated, in both formalin-fixed paraffin-embedded material and plasma. Furthermore, we show that mdPCR can be used to track changes in peripheral blood biomarkers in response to treatment and to detect the emergence of drug-resistant clones. CONCLUSIONS: MdPCR has potential as a tool to detect and quantify tumor-derived mutational events in cell-free DNA from patients with lung cancer.