Interim analysis of the data of non-interventional study to determine the prevalence of EGFR mutations in advanced NSCLC Russian patients (ORTUS).

Abstract

e13109 Background: There is a little information of correlation between EGFRm rate in cytology and plasma samples in Russian NSCLC population. The interim analysis of the study aimed to evaluate the prevalence and types of EGFR mutations in paired cytology and plasma samples in treatment-naive patients with advanced NSCLC. Methods: ORTUS is a multicenter, non-interventional, prospective study to determine EGFR mutations rate in treatmentnaive Russian patients with advanced NSCLC. ClinicalTrials.gov identifier: NCT02321046. The study enrolled 426 patients in stage IIIB / IV of NSCLC. Interim analysis covered the data of 214 cytology verified patients (mean age - 62.6 (range 32-86) years, 58,4% of men) with EGFRm test results in paired cytology and ctDNA samples. 99.5% cases were adenocarcinoma. The proportion of non-smokers/smokers/exsmokers was 46.3%/36%/17.8% respectively. Stage IV disease was in 81% of cases; 84.1% of patients had symptoms. DNA isolation performed using QIAamp DNA FFPE Tissue Kit for cytology and Qiagen Circulating Nucleic Acid Kit for ctDNA according to the manufacturer’s instructions. EGFR gene mutations were analyzed using THerascreen RGQ EGFR PCR Kit in cytology samples and RGQ Plasma EGFR PCR kit in plasma (Qiagen). Results: EGFRm was identified in 17,8% cytology samples (38/214) that is close to 20,2% (1759/8716) in Russian tissue EGFRm study (Imyanitov et al., 2016). 10,3% of paired ctDNA samples were EGFRm positive. Sensitivity and specificity for ctDNA were 42.1%, and 97.1% respectively. The EGFRm rate was 3,9% and 2,6% in smokers, 5,3% and 0% in ex-smokers and 33,3% and 21,2% in nonsmokers in cytology and plasma samples respectively. EGFRm rate and concordance between cytology and ctDNA are presented in a table. EGFRm in ctDNA were detected more frequently in M1a/b groups (p = 0,028). Conclusions: Cytology samples are appropriate for EGFRm testing in NSCLC patients in comparison with tumor tissue ones. High tumor burden (positive metastatic status) is an important factor for successful mutation analysis in ctDNA. [Table: see text]