A newly developed “liquid biopsy” assay that detects free-floating DNA from cells in blood plasma may be an effective tool for detecting mutations in patients with non-small cell lung cancer (NSCLC), according to the results from a recent study.
Liquid biopsies have recently become an attractive alternative to tissue biopsies as a non-invasive method of assessing treatment response, though it is still unclear how effective these methods are.
In a study published in JAMA Oncology, researchers compared one of these tests, the plasma droplet digital polymerase chain reaction (ddPCR) assay, with conventional biopsy testing to determine how effective it was at detecting the EGFR and KRAS mutations in patients with NSCLC.
Led by Geoffrey Oxnard, MD, Dana-Farber Cancer Institute (Boston, MA), researchers looked at 180 patients for the trial: those who were newly diagnosed with advanced, untreated NSCLC (n=120) and those who had developed acquired resistance to an EGFR tyrosine-kinase inhibitor (n=60). All participants received testing with ddPCR and conventional biopsy in order to validate any findings.
The predictive value of plasma ddPCR was found to be 100% for primary EGFR and KRAS mutations, with only a single false-positive reading observed. The results were similar for patients who had an acquired resistance to treatment, where the predictive value was 79%.
The sensitivity of ddPCR fluctuated based on specific mutations but was generally high. A significant association was also observed between test sensitivity and the presence of hepatic or bone metastasis, as well as increasing number of metastatic sites.
In addition, median turnaround time was found to be significantly shorter with ddPCR testing (3 days) than tissue biopsies (12 days for newly diagnosed patients; 27 days for drug-resistant patients).
Researchers concluded that the plasma ddPCR test is ready to be used as a tool to guide clinical decision-making in patients with NSCLC due to its ability to rapidly detect EGFR and KRAS mutations with minimal false-positive results.
