EGFR (hotspots)

NOTE: Our laboratory offers multiple testing options for non-small cell lung cancer. Please see our Lung Cancer overview page.

OVERVIEW

The epidermal growth factor receptor (EGFR) tyrosine kinase is a component of the RAS/RAF/MAPK pathway which is involved in cell proliferation, differentiation, survival, and apoptosis.  Activating EGFR mutations lead to constitutive activation of this pathway, promoting resistance to apoptosis and tumour progression.  Activating mutations include both missense mutations and in-frame deletions or insertions within the tyrosine kinase domain encoded by exons 18 to 21 of the EGFR gene.

In patients with lung non-small cell adenocarcinomas and squamous cell carcinomas in patients with no smoking history, activating mutations in the Epidermal Growth Factor Receptor (EGFR) gene predict a response to anti-EGFR or pan-HER tyrosine kinase inhibitors (TKI).  The mutations detected by this assay are listed in the table below.  Activating EGFR mutations are present in approximately 20% of patients with non-small cell lung cancer in Canada, with 90% of those being either the L858R point mutation in exon 21 or an exon 19 in-frame deletion. 

ExonMutation Detected
18G719X (G719A, G719S, G719D or G719C)
19Detects any of 48 different in-frame deletions
20T790M
S768I
In-frame insertions:
-2319-2320insCAC
-2310-2311insGGT
-2307-2308insGCCAGCGTG (ins9)
21L858R
L861Q
Mutations detected by the Entrogen EGFR Mutation Assay

INDICATION

  • Stage IIIB/IV non-small cell, non-neuroendocrine lung adenocarcinoma
  • Squamous cell lung carcinoma, in patients with no smoking history

TEST REQUIREMENTS

  1. Completed CGL Solid Tumour Testing requisition form
    1. Select “Pretreatment: EGFR (hotspots)”
  2. FFPE Tumour specimen (see Sample Guidelines)
    1. A minimum of 10% tumour content is required

TURN-AROUND TIME

Fourteen calendar days from receipt of specimen and completed, signed requisition form.

RESULTS REPORTING

  • Results are reported as positive or negative for the presence of an EGFR mutation (see table above).
  • Specimens with inadequate tumour tissue may be cancelled by the reviewing pathologist prior to receipt in CGL.

METHOD

Tumour tissue is isolated from the FFPE specimen by macrodissection, followed by extraction of genomic DNA (Promega Maxwell).  Detection of EGFR mutations is performed using the real time PCR based “EGFR Mutation Analysis Kit” from EntroGen according to the manufacturer’s instructions.  This kit uses mutant specific primers and probes to identify EGFR mutations in patient samples that contain both mutant and wild-type DNA. Quantitative amplification and subsequent analysis is performed using an ABI QuantStudio 7 instrument and associated software.  

REFERENCES

Melosky et al. Current Oncology (2018) PMID:29507487