AstraZeneca has presented results from two key studies showing the effectiveness of plasma circulating tumour DNA (ctDNA) testing for epidermal growth factor receptor (EGFR) mutation status in newly diagnosed patients with advanced non-small cell lung cancer (NSCLC) in clinical practice.
Data from the studies — ASSESS and IGNITE — were reported at the European Lung Cancer Conference (ELCC) 2015 in Geneva, Switzerland.
ASSESS — the first large-scale "real world" study comparing tumour biopsy with ctDNA testing for EGFRm in advanced NSCLC — showed concordance between results obtained with the two techniques. In 1162 matched samples, there was good agreement between tumour and plasma test results for EGFRm status (89%, 95%CI 87-91). Plasma testing identified approximately half of patients with EGFRm found by tumour testing, and some patients with EGFR mutations missed by tumour testing were identified as EGFRm by plasma testing.Failure to identify EGFR mutations with tumour testing was associated with use of less sensitive methodology.
Dr Martin Reck, Department of Thoracic Oncology, Lungen Clinic Grosshansdorf, Germany, explained that the study confirms that tumour testing is currently the best way of identifying patients with EGFR mutations but also shows the importance of using sensitive testing methods.
"ASSESS shows that plasma ctDNA testing is a viable alternative to tumour testing when tumour samples are unavailable, provided that optimal DNA extraction and appropriately sensitive methodology are used," he concluded. "It also showed that improvements can still be made in tumour testing, to ensure all patients with an EGFR mutation are identified and given appropriate treatment."
Results of the IGNITE study presented at ELCC 2015 support "real world" EGFR mutation testing in all patients with advanced NSCLC.[2] Using tissue and plasma ctDNA testing in over 3300 patients enrolled from Russia and a number of countries across Asia Pacific including China, researchers found that EGFR mutation frequency in patients with advanced NSCLC of adenocarcinoma (ADC) histology was higher versus non-ADC histology. But they suggested that levels of mutations in non-ADC were sufficient to make testing all patients worthwhile.
In Europe, ctDNA assessment of EGFRm status in patients where a tumour sample is not evaluable was recently approved for use with Iressa (gefitinib), making it the first EGFR tyrosine kinase inhibitor for which ctDNA testing has been included in the label. In February 2015, the China Food and Drug Administration (CFDA) approved an update to the Iressa (gefitinib) label to include blood based diagnostics when tumour tissue is not evaluable.
