CPT® Code 81235

EGFR (epidermal growth factor receptor) (eg, non-small cell lung cancer) gene analysis, common variants (eg, exon 19 LREA deletion, L858R, T790M, G719A, G719S, L861Q)

Molecular genetic testing is a critical procedure used to identify specific mutations in the epidermal growth factor receptor (EGFR) gene, particularly in the context of non-small cell lung cancer (NSCLC). NSCLC is a type of lung cancer that is biologically aggressive and represents 85-90% of all lung cancer cases. The EGFR gene encodes a transmembrane glycoprotein that plays a significant role in cell signaling. When epidermal growth factor binds to these receptors, it triggers a transformation from an inactive monomeric form to an active homodimer form, leading to cellular proliferation and survival. Mutations in the EGFR gene can lead to an overexpression of the receptor and uncontrolled cell growth, which is a hallmark of cancer. Most of the mutations associated with NSCLC occur within four specific exons (18-21) of the EGFR gene. The most prevalent mutation is the exon 19 LREA deletion, which accounts for approximately 47% of cases. Another common mutation is L858R, which is a combination of an exon 19 deletion and a point mutation at exon 21 that substitutes leucine for arginine, representing about 34% of mutations. Additionally, the T790M mutation, which involves a substitution of threonine for methionine at exon 20, is less common but is associated with a poor response to chemotherapy. Other mutations, such as G719A, G719S, and G719C, occur in the kinase domain on exon 18 and account for about 3% of cases. Lastly, the L861Q mutation, where leucine is replaced by glutamine at position 861 on exon 21, is identified in approximately 2% of NSCLC cases. Understanding these mutations is essential for guiding treatment decisions and improving patient outcomes in those diagnosed with NSCLC.