In June of 2016, Roche’s ctDNA-based detection of EGFR mutations in lung cancer patients was the first liquid biopsy to obtain FDA approval. The cobas® EGFR Mutation Test v2 is an automated molecular assay designed to detect the presence of mutations in the EGFR gene in metastatic, non-small cell lung cancer (NSCLC). In normal tissue, the EGFR protein transmits signals in cells to regulate cell growth and cell death. Mutations in the EGFR gene result in abnormal functioning of the EGFR protein and stimulate cancer cell growth in NSCLC.
The first version (v1) of the cobas® EGFR Mutation Test was approved by the FDA in 2013 to detect different specific EGFR mutations in tumor tissue specimens to aid physicians in identifying patients who may be treated first with Tarceva® (erlotinib), which is an EGFR inhibitor drug, called an EGFR tyrosine kinase inhibitor (TKI).
The second version of the test (v2) was approved in late 2015. This approval added another specific EGFR mutation to the other clinically relevant mutations to aid physicians in selecting patients with metastatic NSCLC whose disease has progressed following treatment with EGFR specific drugs (eg, erlotinib) and may be treated with Tagrisso™ (osimertinib).
The 2016 FDA approval of the cobas® EGFR Mutation Test v2 is for both plasma and tissue samples and serves to identify the EGFR gene in the DNA from NSCLC patients. It is intended to be used as an aid in selecting patients with NSCLC for therapy with an EGFR TKI.
Overview of the test:
The cobas® EGFR Mutation Test v2 test identifies 42 mutations in exons 18, 19, 20, and 21 of the EGFR gene using tissue or plasma as a sample. The liquid biopsy test performed on plasma can serve to provide a less invasive testing option and overcomes the limitations of tissue biopsy samples. The test uses a sample preparation system called the cobas-cfDNA Sample Preparation kit which provides stabilization of the cfDNA in the collected specimen. The following is a summary of the test:
- The plasma specimen is prepared using the cobas cfDNA preparation kit which serves to stabilize the cfDNA and prepare the specimen for amplification and detection.
- Following sample preparation, Roche uses the cobas z 480 system for automated amplification and detection.
- The qualitative detection and identification of mutations in exons 18, 19, 20, and 21 of the EGFR gene in DNA is performed using real-time polymerase chain reaction (rtPCR) in the plasma sample obtained from NSCLC patients.
- The test reports out the percent mutations identified in the sample. The percent mutation is reported as a semi-quantitative index (SQI) which can be used to track and identify trends in tumor progression when using frequent serial testing. The result interpretation and test reporting processes are all automated.