Hello, everyone. I'm Dr. Jiayi Shen from Taipei Veterans General Hospital. My topic today is the intrinsic limitation and clinical impact of mutant allele-specific real-time PCR-based EGFR mutation assay in non-small-cell lung cancer. Here is my disclosure. The detection of driver mutations plays a decisive role in the treatment of non-small-cell lung cancer. Patients with driver mutations such as EGFR, ALK, and ROS1 have different treatment strategy and clinical course from those without driver mutations. The mutant allele-specific real-time PCR-based assay, for example, the COBUS EGFR mutation test, is commonly used in current practice. However, it has an intrinsic detection limitation owing to its primer designs. Mutations that were not included in the pre-designed primers cannot be detected. According to our previous study, we found there was a false negative rate of 8.1% for the COBUS test by using center sequencing. Whether the false negative rate will be higher by using a more sensitive test remains unclear. Therefore, we conducted our study. Next-generation sequencing is a more comprehensive technique with wider mutation coverage. We use NGS to determine the false negative rate and intrinsic limitations of the COBUS EGFR mutation test. We focus on the detection rate and patient's clinical outcome. This is a retrospective cohort study conducted in a tertiary medical center in Taiwan. The study period was from January 1, 2012 to July 31, 2020. Patients with stage 4 non-small cell lung cancer EGFR wild type confirmed by the COBUS EGFR test and also OCK IHC wild type were enrolled. The samples were sent for foundation panel. Total 62 patients were enrolled. The median age was 60-year-old. Over two-thirds were male, half were smokers. Adenocardioma accounts for the majority of histology types. Most patients had good performance status. Of the 62 samples, 7 were detected with EGFR mutations by NGS, which means the false negative rate was up to 11.3%. Most were exome 20 insertions. Two patients had received EGFR TKI and had durable response. One patient even received sequential third-generation TKI due to further T790M mutation after treatment. We also evaluate other driver mutations by NGS. We found 64.5% of patients had druggable driver mutations. As mentioned above, 11.3% were EGFR, 8.1% were ROS1, 8.1% were BRAF, 4.8% met exome 14 skipping. KRAS accounted for 21%, and G12C was the predominant type. Other 35.5% of patients had no current druggable driver mutations. However, they had also been found with some clinical significant mutations such as p53 STK11. Take-home message. In our study, we found the COBAS EGFR mutation test had false negative rate 11.3% by NGS in a population with high prevalence of EGFR mutant non-small cell lung cancer. The most overlooked EGFR mutations were exome 20 insertions. A comprehensive molecular analysis in non-small cell lung cancer may impact patients' clinical outcomes. Thank you for your attention.

COBAS EGFR mutation test

limitations

false negative rate

next-generation sequencing

druggable driver mutations