A sensitive and practical method to detect the T790M mutation in the epidermal growth factor receptor

Area of Science:

• Molecular Biology
• Oncology
• Genetics

Background:

• The epidermal growth factor receptor (EGFR) T790M mutation is a key mechanism of resistance to EGFR tyrosine kinase inhibitor (TKI) therapy in non-small cell lung cancer (NSCLC).
• Accurate and sensitive detection of EGFR T790M mutations, especially *de novo* mutations present at low allele frequencies, is crucial for guiding treatment decisions.

Purpose of the Study:

• To develop and validate a rapid, sensitive, and practical method for detecting the EGFR T790M mutation.
• To assess the prevalence of *de novo* EGFR T790M mutations in TKI-naïve NSCLC patients with activating EGFR mutations.
• To investigate the association between *de novo* T790M mutations and clinical outcomes of EGFR-TKI treatment.

Main Methods:

• Development of a one-step allele-specific competitive blocker (ACB) combined with TaqMan quantitative polymerase chain reaction (PCR) amplification refractory mutation system (ARMS) assay.
• Performance evaluation using a human genomic DNA panel with serially diluted mutant alleles.
• Application of the ACB-ARMS PCR method to TKI-naïve NSCLC patient samples harboring EGFR-activating mutations.

Main Results:

• The ACB-ARMS PCR method demonstrated high sensitivity, detecting mutations at allele frequencies as low as 0.01%.
• The assay identified EGFR T790M mutations in 6 out of 27 (22.2%) TKI-naïve NSCLC patients, a significantly higher detection rate compared to scorpion ARMS (0%).
• No significant association was found between *de novo* T790M mutations and clinical variables, progression-free survival, or overall survival, although a trend towards shorter survival was observed in mutant patients.

Conclusions:

• The ACB-ARMS PCR method is a sensitive and practical tool for detecting low-frequency EGFR T790M mutations in clinical settings.
• The clinical significance of *de novo* EGFR T790M mutations in NSCLC warrants further investigation.
• This method can aid in the early identification of potential TKI resistance mechanisms in NSCLC patients.