title: Detection of epidermal growth factor receptor mutation in lung cancer by droplet digital polymerase chain reaction.
abstract: BACKGROUND
  Two types of epidermal growth factor receptor (EGFR) mutations in exon 19 and exon 21 (ex19del and L858R) are prevalent in lung cancer patients and sensitive to targeted EGFR inhibition. A resistance mutation in exon 20 (T790M) has been found to accompany drug treatment when patients relapse. These three mutations are valuable companion diagnostic biomarkers for guiding personalized treatment. Quantitative polymerase chain reaction (qPCR)-based methods have been widely used in the clinic by physicians to guide treatment decisions. The aim of this study was to evaluate the technical and clinical sensitivity and specificity of the droplet digital polymerase chain reaction (ddPCR) method in detecting the three EGFR mutations in patients with lung cancer.
  
  
  METHODS
  Genomic DNA from H1975 and PC-9 cells, as well as 92 normal human blood specimens, was used to determine the technical sensitivity and specificity of the ddPCR assays. Genomic DNA of formalin-fixed, paraffin-embedded specimens from 78 Chinese patients with lung adenocarcinoma were assayed using both qPCR and ddPCR.
  
  
  RESULTS
  The three ddPCR assays had a limit of detection of 0.02% and a wide dynamic range from 1 to 20,000 copies measurement. The L858R and ex19del assays had a 0% background level in the technical and clinical settings. The T790M assay appeared to have a 0.03% technical background. The ddPCR assays were robust for correct determination of EGFR mutation status in patients, and the dynamic range appeared to be better than qPCR methods. The ddPCR assay for T790M could detect patient samples that the qPCR method failed to detect. About 49% of this patient cohort had EGFR mutations (L858R, 15.4%; ex19del, 29.5%; T790M, 6.4%). Two patients with the ex19del mutation also had a naïve T790M mutation.
  
  
  CONCLUSIONS
  These data suggest that the ddPCR method could be useful in the personalized treatment of patients with lung cancer.
authors.affiliation: Translational Bioscience and Diagnostics, WuXi AppTec, Shanghai, People's Republic of China.
authors.forename: Qing
authors.initials: Q
authors.lastname: Xu
authors.affiliation: Department of Pathology, Guangdong Provincial Hospital of TCM, Guangzhou University of Chinese Medicine, Guangdong Provincial Academy of Chinese Medical Sciences, Guangzhou, People's Republic of China.
authors.forename: Yazhen
authors.initials: Y
authors.lastname: Zhu
authors.affiliation: Translational Bioscience and Diagnostics, WuXi AppTec, Shanghai, People's Republic of China.
authors.forename: Yali
authors.initials: Y
authors.lastname: Bai
authors.affiliation: Translational Bioscience and Diagnostics, WuXi AppTec, Shanghai, People's Republic of China.
authors.forename: Xiumin
authors.initials: X
authors.lastname: Wei
authors.affiliation: Department of Pathology, Guangdong Provincial Hospital of TCM, Guangzhou University of Chinese Medicine, Guangdong Provincial Academy of Chinese Medical Sciences, Guangzhou, People's Republic of China.
authors.forename: Xirun
authors.initials: X
authors.lastname: Zheng
authors.affiliation: Translational Bioscience and Diagnostics, WuXi AppTec, Shanghai, People's Republic of China.
authors.forename: Mao
authors.initials: M
authors.lastname: Mao
authors.affiliation: Department of Pathology, Guangdong Provincial Hospital of TCM, Guangzhou University of Chinese Medicine, Guangdong Provincial Academy of Chinese Medical Sciences, Guangzhou, People's Republic of China.
authors.forename: Guangjuan
authors.initials: G
authors.lastname: Zheng
keywords: L858R; T790M; companion diagnostics; ddPCR; ex19del