Qing Zhou¹, Zhi-hong Chen², Qiu-yi Zhang², Jian Su², Jin-ji Yang², Chong-rui Xu², Yi-chen Zhang², Wen-zhao Zhong², Yi-long Wu² 

¹Division 3 of Pulmonary Oncology, Guangdong Lung Cancer Institute, Guangdong General Hospital and Guangdong Academy of Medical Sciences, ²Guangdong Lung Cancer Institute, Guangdong General Hospital and Guangdong Academy of Medical Sciences. 

Objective:Activating mutations in the gene encoding EGFR occur primarily in non-small cell lung cancer (NSCLC) and result in constitutive activation of the kinase activity of the EGFR protein, thereby contributing to the oncogenic process. The prevalence of these mutations occurs in up to 50% of patients in non-smoking/light-smoking female patients of Asian descent with adenocarcinoma. Clinical data indicate that patients with advanced NSCLC tumors harboring EGFR-activating mutations, which occur most commonly as deletions in exon 19 or as the L858R point mutation in exon 21, exhibit a high response rate and prolonged progression-free survival (PFS) when treated with EGFR-tyrosine kinase inhibitors (TKIs). Genotyping becomes essential for the management of lung cancer and the conventional biopsy and tumor tissue testing is the only way to determine the EGFR mutation status of a patient. However, a substantial number of patients in China miss the opportunity to receive the life-changing medicine because they are poor candidates for biopsy or with limited tissue for molecular testing. A surrogate tissue, such as plasma, that contains circulating free tumor DNA (cfDNA) can potentially reflect the tumor EGFR mutation status and can be collected in a relatively non-invasive manner. EGFR mutations detected in plasma can be used to diagnose the presence of sensitizing and resistance mutations in patients without tumor tissue (or prior to a tissue-based EGFR result). Several studies in NSCLC and colorectal cancer have demonstrated the possible utility of cfDNA for the detection of EGFR or KRAS mutations. The cobas^®plasma assay is in development to detect the EGFR mutation in cfDNA from peripheral blood and is expected to work as an alternative EGFR testing in clinical practice. Its diagnosistic utility comparing to tissue testing, the golden standard, needs to be further demonstrated. Our objective is to assess the diagnostic utility for the detection of EGFR mutations by the cobas^® plasma assay in advanced NSCLC patients compared with paired tumor testing. Method: We plan to enroll approximately 100 NSCLC patients in the study where approximately 50 patients with sensitizing EGFR mutations and 50 patients with EGFR wild type. Retrospective and paired EGFR mutation testing of tissue and plasma will be performed with amplification refractory mutation system (ARMS) and cobas^® EGFR blood test (in Development), respectively. The primary end point is to calculate the sensitivity, specificity, predictive positive value, predictive negative value and concordance of results from cobas® plasma assay compared to ARMS assay. Tumor samples and paired peripheral blood samples were both collected at baseline for EGFR genotyping. Each blood specimen was collected into one 4-ml EDTA-containing vacutainer and was spun twice into plasma (4℃, 3000 rpm, 5 min;4℃, 16,000×g, 10 min) within 4 hours of collection. cfDNA was extracted from 2ml of plasma by using the cobas^® plasma assay and the final DNA eluent was frozen at-20℃ until genotyping. Written informed consent regarding specimen collection was obtained from all patients. Result: Now the ARMS-based EGFR genotyping for tissue is ongoing and the preliminary results will be updated in this CSCO. Conclusion: Now the ARMS-based EGFR genotyping for tissue is ongoing and the preliminary results will be updated in this CSCO.

Key Words: NSCLC  EGFR mutations  cfDNA detection