Evaluation of liquid based cytology in detection of EGFR mutation in NSCLC by large samples

Cytology samples are the main resources to detect driver oncogene alterations for advanced lung cancer patients. To explore the value of liquid-based cytology in the detection of epidermal growth factor receptor (EGFR) mutation in non-small cell lung cancer (NSCLC), we analyzed data from a large cohort of EGFR mutation-positive patients.

We analyzed the clinicopathological characteristics of 8,029 NSCLC cases tested for EGFR mutation by liquid-based cytology specimens and 1,934 NSCLC cases tested by formalin-fixed and paraffine-embedded (FFPE) samples in the Shanghai Pulmonary Hospital from September 2015 to December 2019. Before detection, we evaluated the number of tumor cells in the liquid-based cytology slide, and samples with more than 50 tumor cells and visible sediment were selected for DNA extraction after centrifugation.

The positive rate of EGFR mutation in liquid-based cytology-tested cases was 47.18%, higher than the 41.37% tested through FFPE sample (P<0.01). Accordingly, the mutation rate of EGFR in adenocarcinoma (AC) and NSCLC was higher than that of the FFPE sample (60.01% vs. 54.15%, P<0.01; 30.54% vs. 21.99%, P<0.01). The positive rate of EGFR mutation in pleural effusion was 62.67%, which was the highest rate among liquid-based cytology sample t (P<0.01).

Using quality control and standard procedure, it was found that liquid-based cytology specimen testing is a convenient and reliable method of EGFR detection, as validated by analysis of a large cohort. EGFR mutation detection should also be carried out in NSCLC patients diagnosed by cytology more than in AC patients.