Liquid Biopsy EGFR

Function

Liquid Biopsy for EGFR (Epidermal Growth Factor Receptor) is a non-invasive test that analyzes circulating tumor DNA (ctDNA) shed into the blood by cancerous cells. EGFR is a protein on the surface of cells that helps them grow. In certain types of cancer, particularly Non-Small Cell Lung Cancer (NSCLC), mutations in the EGFR gene cause the receptor to be permanently 'on,' leading to rapid cell proliferation. This 'liquid' approach allows for genetic profiling of the tumor without the need for a traditional, invasive tissue biopsy.

Why it is Ordered

This test is a cornerstone of precision medicine in lung cancer. It is ordered to:

• Identify actionable mutations (like Exon 19 deletions or L858R) in patients where tissue biopsy is difficult or impossible.
• Monitor patients currently on EGFR-Tyrosine Kinase Inhibitors (TKIs) for the development of resistance mutations, specifically the T790M or C797S mutations.
• Track the 'molecular response' to treatment in real-time.
• Screen for recurrence in patients who have previously completed treatment.

Associated Conditions

The test is specifically associated with Non-Small Cell Lung Cancer (NSCLC). The detection of sensitizing EGFR mutations indicates that the patient is a candidate for first- or second-generation TKIs (like Erlotinib or Gefitinib) or third-generation TKIs (like Osimertinib). Liquid biopsy is particularly revolutionary because tumors are heterogeneous; a single tissue biopsy might miss a mutation that a liquid biopsy—which captures DNA from all tumor sites in the body—might detect.