Prevalence and breakdown of EGFR exon 20 driver mutations in routine NHS lung cancer diagnostic testing

In non-small cell lung cancer (NSCLC), oncogenic driver mutations in epidermal growth factor receptor ( EGFR ) typically occur in exons 18, 19, 20 and 21.1 Until recently, EGFR -driven tumours displaying sensitivity to EGFR tyrosine kinase inhibitors (TKIs) have almost exclusively comprised those with activating mutations in exons 18, 19 and 21, while tumours with primary activating mutations located within exon 20, and particularly those with insertions or deletion–insertions, largely appeared to be resistant to TKIs.2 For this reason, single-gene tests such as quantitative PCR (qPCR)-based assays performed as part of standard clinical diagnostic testing have understandably focused predominantly on the most common driver mutations within exons 18, 19 and 21, which are known to confer TKI sensitivity. Novel therapeutic agents for patients with EGFR exon 20 insertions are currently in trials, and as such, determining the frequency and diversity of exon 20 mutations in the NSCLC population may be highly relevant to future clinical practice.3 Since data from most qPCR-based EGFR tests are unlikely to identify and will not classify the full spectrum of exon …