EGFR T790M (Tissue)

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

OVERVIEW

Non-small cell lung cancers with activating EGFR mutations commonly develop acquired resistance to first- and second-generation anti-EGFR TKI therapies.  In approximately 50-60% of cases, development of the secondary T790M mutation in EGFR is responsible for TKI therapy resistance. However, the T790M mutation has been shown to remain sensitive to treatment with osimertinib. 

INDICATION

  • Non-small cell lung adenocarcinoma progressing on first-line EGFR TKI therapy

TEST REQUIREMENTS

  1. Completed CGL Solid Tumour Testing requisition form
    1. Select: Progression: Tissue biopsy
    2. In Reason for Testing/Clinical History, indicate the EGFR activating mutation detected at diagnosis if this testing was not performed at CGL.
  2. FFPE Tumour specimen (see Sample Guidelines)
    1. Tissue should be collected post-progression
    2. A minimum of 10% tumour content is required

TURN-AROUND TIME

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

METHOD

Tumour tissue is isolated from the FFPE specimen by macrodissection, followed by extraction of genomic DNA (Promega Maxwell).  Quantitative amplification is performed with primers and probes specific to EGFR T790M, L858R, G719X, and most exon 19 deletions, followed by analysis using the Biorad QX200 Droplet Digital PCR System. 

RESULTS REPORTING

  • Results are reported as positive or negative for the presence of the EGFR T790M mutation and for the initial activating mutation in the tumour (if known and detectable by this assay)
  • Failed testing may be repeated at the discretion of the laboratory if sufficient sample remains.
  • Specimens with inadequate tumour tissue will be cancelled by the reviewing pathologist prior to testing.

REFERENCES

  1. Melosky et al. Current Oncology (2018) PMID:29507487
  2. Mok et al. New England Journal of Medicine (2017) PMID:27959700