A new test, the first to combine liquid biopsy and next generation sequencing (NGS), has been approved by the US Food and Drug Administration (FDA) for use in patients with metastatic nonsmall cell lung cancer (NSCLC) to identify tumors with specific mutation types of the epidermal growth factor receptor (EGFR) gene.
The Guardant360 CDx assay (Guardant Health) is the first to combine the two technologies into a diagnostic test to guide treatment decisions.
Liquid biopsy offers the advantage of obtaining genetic information on a tumor from a simple blood draw instead of a tissue biopsy, which requires fine-needle aspiration of the lung. “It is less invasive and more easily repeatable in comparison to standard tissue biopsies…and can be used in cases in which standard tissue biopsies are not feasible, for instance, due to the location of the tumor,” the FDA commented.
NGS offers the advantage of simultaneously detecting mutations in 55 tumor genes, as opposed to conducting a separate test for each gene.
However, although the assay can provide information on multiple solid tumor biomarkers, the approval is specific only to identifying EGFR mutations in patients who will benefit from treatment with osimertinib (Tagrisso, AstraZeneca).
The approval does not validate the test for use in detecting other biomarkers, the FDA noted.
As previously reported, the assay has a comprehensive NGS panel that identifies seven guideline-recommended predictive biomarkers (EGFR, ALK, ROS1, BRAF, RET, MET, ERBB2) — known as the G7 biomarkers — and one prognostic marker (KRAS).
But the FDA noted that “genomic findings for other biomarkers evaluated are not validated for choosing a particular corresponding treatment with this approval.”
“If the specific NSCLC mutations associated with today’s approval are not detected in the blood, then a tumor biopsy should be performed to determine if the NSCLC mutations are present,” the agency emphasized.
Nevertheless, the FDA announcement highlights the potential of the test to identify these other biomarkers.
“Approval of a companion diagnostic that uses a liquid biopsy and leverages next generation sequencing marks a new era for mutation testing,” Tim Stenzel, MD, PhD, director of the Office of In Vitro Diagnostics and Radiological Health in the FDA’s Center for Devices and Radiological Health, commented in a statement.
“In addition to benefitting from less invasive testing, patients are provided with a simultaneous mapping of multiple biomarkers of genomic alterations, rather than one biomarker at a time, which can translate to decreased wait times for starting treatment and provide insight into possible resistance mechanisms,” he noted.
The manufacturer also highlighted this potential. “We are confident that our FDA approval will help accelerate wider adoption of guideline-recommended genomic profiling, increase the number of advanced cancer patients who receive potentially life-changing treatments, and pave the way for new companion diagnostic developments for the Guardant360 CDx,” said Helmy Eltoukhy, PhD, CEO of Guardant Health, in a statement.
The FDA did not cite any specific trial of the assay in its announcement of the approval, but Medscape Medical News has previously reported results from the NILE study presented at the 2019 Annual Meeting of the American Association for Cancer Research (AACR).
The NILE trial was conducted in 282 patients with untreated nonsquamous NSCLC who underwent standard-of-care tissue genotyping and had a pretreatment blood sample for cell-free DNA (cfDNA) analysis.
Results showed that a G7 biomarker was identified in a significantly higher proportion of liquid biopsies compared with tissue genotyping (27.3% vs 21.3%; P < .0001).
The lower frequency of G7 biomarkers in tissue genotyping was due to insufficient tissue for sequential sequencing, the authors reported at that time.
Liquid biopsy improved G7 detection frequency by 48%, from 60 to 89 patients, which included samples that were negative by tissue testing (7), not tested (16), or lacked sufficient sample for a tissue-based test (6).
Of 193 patients without a G7 biomarker by tissue or cfDNA, 24 patients (12.4%) had an activating KRAS mutation identified in the tissue alone, and with cfDNA, KRAS-positivity increased from 24 to 92 patients.
The Guardant360 CDx assay has been granted a breakthrough device designation, whereby the FDA provides intensive interaction and guidance on efficient device development to the company.
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