EGFR

Mutations of the epidermal growth factor receptor ( EGFR) are used to predict sensitivity of tumor cells to EGFR-tyrosine kinase inhibitors (EGFR-TKI, also called “EGFR inhibitors”), such as Gefitinib and Erlotinib.

EGFR is widely recognized for its importance in cancer. Amplification and mutations have been shown to be driving events in many cancer types. Its role in non-small cell lung cancer (NSCLC), glioblastoma and basal-like breast cancers has spurred many research and drug development efforts. In normal cells, the EGFR is only activated on binding of the cognate ligand to the receptor, however, in tumor cells carrying a mutation in the adenosine triphosphate (ATP)-binding pocket of the kinase domain (exons 18–21) of the EGFR, the receptor is constitutively activated. It has been postulated that these mutations cause structural alterations that destabilize the autoinhibited conformation of the receptor normally assumed in the absence of ligand binding.1)

As a consequence of improper activation, tumor cells acquire a malignant phenotype characterized by abnormal cell survival and proliferation. Tyrosine kinase inhibitors have shown efficacy in EGFR amplfied tumors, most notably Gefitinib and Erlotinib.2)

The later generation TKI's have seen some success in treating these resistant cases, and targeted sequencing of the EGFR locus has become a common practice in treatment of non-small cell lung cancer. Exon sequencing of genomic DNA revealed missense and deletion mutations in the EGFR gene within exons 18 through 21 of the kinase domain.3)

The EGFR mutations show a striking correlation with patient characteristics. Mutations were more frequent in women (20%) than in men (9%), and more frequent in the patients from Japan (26%) than in those from the United States (3%). Notably, the patient characteristics that correlate with the presence of EGFR mutations are those that correlate with clinical response to gefitinib treatment.4)

EGFR mutations, such as the L858R point mutation in exon 21 and the in-frame deletional mutation in exon 19, have been definitively associated with response to EGFR-TKIs.5)

Test Description:

The analysis of common variants in the EGFR gene is detected by automated DNA sequencing. The gene is analyzed by PCR-based double-stranded automated sequencing in the sense and antisense directions. The variations detected are the following:

EGFR Variations
EGFR Exon SNP number Variation
18 rs28929495 G719X
19 rs121913438 L702_P708delinsS
20 rs121434569 T790M
21 rs121434568 L858R
21 rs121913444 L861Q

Specimen Requirements:

  • Specimen and Volume: Buccal epithelial cells collected on standard cotton tip swabs. Alternative acceptable specimens include 3-5 cc of blood in EDTA or ACD BD Vacutainer tubes guide. Other types of tissue may be accepted (please call 818-789-1033 to verify before sending).
  • Contact your doctor's office or FirmaLab for buccal swab kits. Buccal Swab Kit Instructions
  • Temperature: can be at room temperature the specimen needs to be at the laboratory no more then 72hrs. Do not freeze whole blood.
  • Turn around time: 5-7 days

Specimen Rejection Criteria: Below are general rejection criteria. If the specimen must be rejected based on the following criteria, or specific criteria for the requested test:

  1. The test requisition form has missing information. Requisition must contain the required information including:
    • Requesting party and referring authority, usually a healthcare professional.
    • Patient identifying information - Name or alias if anonymous;
    • Test requested, Clinical indication for testing;
    • Date and time of specimen collection;
    • Type of sample (e.g. whole blood or epithelial cells obtained by buccal swab);
    • All other identifying information (e.g. social security number, telephone number, hospital ID, sex … etc.) is optional, but useful for accurate differentiating between patients with similar names.
  2. Label is unclear;
  3. Blood specimen is from a recipient of bone marrow transplant;
  4. Specimen is inappropriate for test requested;
  5. Blood sample is clotted or hemolyzed;
  6. Incorrect container or Vacutainer used
1)
Zhang, W, Stabile, LP, Keohavong, P et al. Mutation and polymorphism in the EGFR-TK domain associated with lung cancer. J Thorac Oncol. 2006; 1: 635–647.
2)
Kobayashi S, et. al.. EGFR Mutation and Resistance of Non–Small-Cell Lung Cancer to Gefitinib. N Engl J Med 2005; 352:786-792. DOI: 10.1056/NEJMoa044238
3)
Paez G, et. al.. EGFR Mutations in Lung Cancer: Correlation with Clinical Response to Gefitinib Therapy. Science 2004; 304:1497-1500. DOI: 10.1126/science.1099314
4)
Paez G, et.al.. EGFR Mutations in Lung Cancer: Correlation with Clinical Response to Gefitinib Therapy. Science 2004; 304:1497-1500. DOI: 10.1126/science.1099314
5)
De Pas T, et. al.. Activity of Epidermal Growth Factor Receptor-Tyrosine Kinase Inhibitors in Patients with Non-small Cell Lung Cancer Harboring Rare Epidermal Growth Factor Receptor Mutations. Journal of Thoracic Oncology 2011; 6:1895-1901. DOI: https://doi.org/10.1097/JTO.0b013e318227e8c6
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