EGFR mutations detection on liquid-based cytology: is microscopy still necessary?

Area of Science:

• Oncology
• Molecular Diagnostics
• Cytopathology

Background:

• Liquid-based cytology (LBC) is increasingly used for non-small cell lung cancer (NSCLC) diagnosis.
• Accurate detection of epidermal growth factor receptor (EGFR) mutations is crucial for NSCLC treatment decisions.
• Molecular testing of cytology samples presents challenges in DNA yield and purity.

Purpose of the Study:

• To compare molecular techniques for detecting EGFR mutations in LBC samples.
• To evaluate the impact of laser capture microdissection (LCM) on EGFR mutation detection rates.
• To identify the most efficient and accurate method for EGFR mutation testing in LBC.

Main Methods:

• DNA extraction from 58 LBC samples, directly from CytoLyt solution and after Papanicolaou staining with LCM.
• EGFR mutation detection using direct sequencing, high-resolution melting analysis, fragment analysis, and TaqMan assays.
• Comparison of mutation detection rates between direct and LCM-derived DNA samples.

Main Results:

• Direct sequencing showed discordant EGFR mutation rates: 10.3% (CytoLyt-derived) vs. 17.2% (LCM-derived).
• High-resolution melting analysis, fragment analysis, and TaqMan assays achieved a consistent 17.2% mutation rate on matched samples.
• Non-sequencing methods performed directly on CytoLyt-derived DNA yielded higher and consistent mutation detection rates.

Conclusions:

• LCM and direct sequencing may not be optimal for EGFR mutation detection in LBC.
• Sensitive, non-sequencing molecular assays directly on CytoLyt-derived DNA offer a faster, easier, and standardized approach.
• This improved methodology enhances EGFR testing standardization for LBC in NSCLC diagnosis.