Abstract B02: Liquid biopsy for screening of driver mutations in EGFR gene: Personalized medicine for use tyrosine kinase inhibitors in non-small cell lung cancer patients

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Abstract Non-small cell lung cancer (NSCLC) accounts for approximately 85% of all lung cancers worldwide. In Brazil there were an estimated 28.220 new cases in 2016. The 5-year survival rate in advanced NSCLC patients is less than 5%, making necessary the development of diagnostic strategies to improve the treatment and survival of these patients. Activating mutations of epidermal growth factor receptor (EGFR) gene occur in approximately 10–15 % in Caucasian and approximately 30% in Brazilian NSCLC cases. The first- and second-generation of EGFR tyrosine kinase inhibitors (TKIs) have been widely used for advanced NSCLC patients who are eligible for the treatment. Liquid biopsies using plasma-derived cell-free DNA (cfDNA) is an emerging noninvasive test allowing a better selection and monitoring of NSCLC. The aim of this study was to evaluate the frequency of EGFR mutations using liquid biopsy samples before and after TKIs treatment in a cohort of NSCLC Brazilian patients. All the patients were investigated for EGFR mutations by real-time qPCR Cobas© EGFR Mutation Test v2. Clinical data were obtained prior to blood collection from physician and/or pathologists involved in the original diagnoses. Blood samples were collected at Progenetica Laboratory or sent from other laboratories, centrifuged immediately for the plasma separation, and frozen. Fisher´s exact test was calculated to compare frequency distribution between two groups (GraphPad Prism version 6.00). This study enrolled 535 NSCLC Brazilian patients from Southeast+South (74.9%), North+Northeast (8.8%), and Midwest+Federal District (4.7%). Regional information was missing for 11.3% of cases. As expected, NSCLC was more frequent among women (56.4%) compared to men (43.6%). Four hundred cases (74.8%) did not show any EGFR mutations; however, 135 cases presented 19Del (57.8%), L858R (16.3%), double 19Del; T790M (11.1%), double T790M; L858R (8.15%), G719X (2.9%), L861Q (1.48%), 20Ins, triple L858R; T790M; 20Ins and S768I; G719X (0.74% each one) mutations spanning 18, 19, 20, and 21 EGFR exons. Previous results from liquid biopsy for EGFR mutation were obtained for 75/535 cases (14%). Among these patients, 10/75 cases (13.3%) presented nondetected mutations. Deletions at exon 19 (19Del) and mutations at exon 21 (L858R) were the most frequent, accounting for 61.5% and 23%, respectively. Since 19Del and L858R are drug-sensitive mutations, we compared the frequency of EGFR mutations in patients before and after TKIs treatment. Interestingly, patients harboring drug-sensitive mutations before the treatment were negative for the presence of 19Del (37.5%) and L858R (66.7%) after the treatment, respectively (p<0.0001). In addition, EGFR T790M mutation already associated with drug resistance was identified in 3/65 (4.6%) of cases in double with 19Del before the TKIs treatment. After treatment, one patient was negative and two patients remained positive for both mutations, respectively. These results showed that liquid biopsy based on cfDNA is a powerful tool for personalized medicine for early detection, stratification, and monitoring of EGFR druggable mutations in NSCLC patients. The presence of cfDNA has been related to aggressiveness and poor prognosis of NSCLC patients, and it is important to note that not all cases have the tumor cfDNA. To our knowledge this is the first report showing the application of liquid biopsies for management of NSCLC patients in Brazil. Clinical data collection is under way for better reliability results. High index of nondetected results was observed in this study; however, new protocols using more sensitive methodologies such as next-generation sequencing and digital PCR are under development in our institution to improve the sensitivity of this test. Citation Format: Priscila D. R. Cirillo, Natália P. Lopes, Carolina Bustamante, Agatha A. Morais, Natália L. Viana, Camila S. Portella, Elvis C. C. Mateo, Maíra C. M. Freire, Mariano G. Zalis. Liquid biopsy for screening of driver mutations in EGFR gene: Personalized medicine for use tyrosine kinase inhibitors in non-small cell lung cancer patients [abstract]. In: Proceedings of the AACR International Conference held in cooperation with the Latin American Cooperative Oncology Group (LACOG) on Translational Cancer Medicine; May 4-6, 2017; São Paulo, Brazil. Philadelphia (PA): AACR; Clin Cancer Res 2018;24(1_Suppl):Abstract nr B02.