Abstract: Detection of EGFR Mutations in Peripheral Blood and Its Clinical Significance in Lung CancerPatientsQunxin PENG1, Jin ZHAO1, Hualong QIN2, Binghua YANG1Correspondence to: Binghua YANG, E-mail: ybh8527@163.com1Department of Clinical Laboratory, The First Affiliated Hospital of Soochow University, Suzhou 215006, China2Cardiothoracic Surgery, The First Affiliated Hospital of Soochow University, Suzhou 215006, ChinaThis work was supported by Suzhou Municipal Planning Project of Science and Technology (No.YJS0921)Abstracts Objective: To screen for epidermal growth factor receptor (EGFR) mutations in lung cancer patients and to investi-gate the characteristics of EGFR mutations as well as the clinical significance through the detection of somatic mutations in EGFR inthe DNA circulating in plasma. Methods: DNA was extracted from the serum of 96 lung cancer patients and the homologous tumorsamples of 59 of these patients. EGFR gene mutations were detected by PCR amplification and gene sequencing analysis. Results: So-matic mutations in EGFR were identified in plasma from 17 of the 96 samples ( 17.7 % ), including 15 cases ( 88.2 % ) with mutationsin exon 19 and 2 cases ( 11. 8 % ) with mutations in exon 21. Among the 17 mutations detected, 3 homozygous mutations ( i.e. 2 L858Rand 1 del E746-A7502 samples ) and 14 heterozygous mutations were detected by direct sequencing. Monoclonal antibody sequenc-ing was used to further determine the types of mutations in the 14 heterozygous mutation samples ( 9 del E746-A7502, 3 delE746-A750(1) and 2 del L747-S752 samples ). The results showed that the patients with lung adenocarcinoma (including adenosqua-mous carcinoma) had an increased frequency of mutations and that the mutation was not closely correlated with gender or smoking his-tory. Further analysis of these 59 patients demonstrated that the EGFR mutation detected in plasma was consistent with that detected intumor tissue, suggesting that the EGFR mutations in plasma originated from the primary tumor. Conclusion: The EGFR mutations de-tectable in DNA circulating in plasma are in accordance with those in lung cancer samples. In addition, compared with direct sequenc-ing, the“Gold Standard”method, monoclonal antibody sequencing can more precisely determine the type of mutation. The detection ofmutated EGFR DNA circulating in plasma, a simple and minimally invasive procedure, can be applied to the clinical detection of EGFRmutations, thus assisting in the prediction of the efficacy of targeted therapy.Keywords Lung cancer; Plasma; Circulating DNA; Epidermal growth factor receptor; Targeted therapy