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Multinational proficiency tests for EGFR exon 20 insertions reveal that the assay design matters
Michaela A Ihle1, Carina Heydt2, Anne Maria Schultheis2
1Institute of Pathology, University of Cologne, Faculty of Medicine and University Hospital Cologne, Kerpener Str. 62, 50924, Cologne, Germany. michaela.ihle@uk-koeln.de.
Abstract:
Insertion mutations in exon 20 of the epidermal growth factor receptor gene (EGFR exon20ins) are rare, heterogeneous alterations observed in non-small cell lung cancer (NSCLC). With a few exceptions, they are associated with primary resistance to established EGFR tyrosine kinase inhibitors (TKIs). As patients carrying EGFR exon20ins may be eligible for treatment with novel therapeutics-the bispecific antibody amivantamab, the TKI mobocertinib, or potential future innovations-they need to be identified reliably in clinical practice for which quality-based routine genetic testing is crucial. Spearheaded by the German Quality Assurance Initiative Pathology two international proficiency tests were run, assessing the performance of 104 participating institutes detecting EGFR exon20ins in tissue and/or plasma samples. EGFR exon20ins were most reliably identified using next-generation sequencing (NGS). Interestingly, success rates of institutes using commercially available mutation-/allele-specific quantitative (q)PCR were below 30% for tissue samples and 0% for plasma samples. Most of these mutation-/allele-specific (q)PCR assays are not designed to detect the whole spectrum of EGFR exon20ins mutations leading to false negative results. These data suggest that NGS is a suitable method to detect EGFR exon20ins in various types of patient samples and is superior to the detection spectrum of commercially available assays.
Insights
Accurate detection of epidermal growth factor receptor (EGFR exon20ins) mutations in non-small cell lung cancer is vital for targeted therapy. Next-generation sequencing (NGS) proved superior to PCR methods in identifying these rare mutations.
Area of Science:
- Oncology
- Genetics
- Molecular Diagnostics
Background:
- Epidermal growth factor receptor (EGFR) exon 20 insertion mutations (EGFR exon20ins) are rare in non-small cell lung cancer (NSCLC).
- These mutations confer primary resistance to standard EGFR tyrosine kinase inhibitors (TKIs).
- Accurate identification of EGFR exon20ins is critical for patient eligibility for novel therapies like amivantamab and mobocertinib.
Purpose of the Study:
- To assess the performance of different genetic testing methods for detecting EGFR exon20ins.
- To evaluate the reliability of routine diagnostic tests in identifying these specific mutations in clinical practice.
Main Methods:
- Two international proficiency tests were conducted involving 104 institutes.
- Participants analyzed tissue and/or plasma samples for EGFR exon20ins.
- Methods assessed included next-generation sequencing (NGS) and mutation-/allele-specific quantitative PCR (qPCR).
Main Results:
- Next-generation sequencing (NGS) demonstrated the highest reliability in detecting EGFR exon20ins.
- Mutation-/allele-specific qPCR assays showed low success rates (<30% for tissue, 0% for plasma).
- Many qPCR assays are not designed to detect the full spectrum of EGFR exon20ins, leading to false negatives.
Conclusions:
- NGS is a suitable and superior method for detecting EGFR exon20ins across various sample types.
- Current commercially available mutation-/allele-specific qPCR assays have limitations in detecting the full range of EGFR exon20ins.
- Quality-based routine genetic testing using NGS is crucial for identifying NSCLC patients eligible for targeted therapies.
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