External quality assessment for EGFR exon 20 mutation testing in patients with non-small cell lung cancer in Spain

Non-small cell lung cancer (NSCLC) can arise from insertions in exon 20 of the EGFR gene, among other alterations. We carried out an external quality assessment (EQA) to evaluate the accuracy of laboratory methods and to highlight the importance of detecting and identifying genetic alterations, such as EGFR exon 20 insertion, in patients with NSCLC.

The 2021 EGRF exon 20 EQA program consisted of two rounds, in which four formalin-fixed paraffin-embedded specimens (round 1: two positive for EGFR exon 20 insertions/duplications, one positive for a common EGFR alteration, and one wild-type; round 2: three positive for EGFR exon 20 insertions/duplications and one wild-type) obtained from patients with NSCLC were tested.

Approximately 80% of the invited laboratories participated in each round. The most common DNA isolation techniques used were the cobas® DNA Sample Preparation Kit (46.7%) in round 1 and QIAamp (37.1%) in round 2. The most frequently used genotyping method in both rounds was the cobas® EGFR Mutation Test (round 1: 53.3%; round 2: 37.1%). In both rounds, 71.1% and 73.6% of the tests, respectively, reported the expected result. The lowest success rate was observed in the H773delinsRY Exon 20 determination (round 1: 17.8%; round 2: 31.4%). This alteration was correctly determined only by next-generation sequencing.

The variability in the genotyping methods and the success rate obtained in our study highlight the importance of EQA in Spain to ensure high performance.