title: EGFR array: uses in the detection of plasma EGFR mutations in non-small cell lung cancer patients.
abstract: BACKGROUND
  We aim to develop a simple and sensitive array-based method for the detection of epidermal growth factor receptor (EGFR) gene mutations in the plasma of non-small-cell lung cancer patients and determine its use in the follow-up of those on tyrosine-kinase inhibitor (TKI) therapy.
  
  
  METHODS
  DNA from 100 μl of plasma was amplified in the presence of peptide nucleic acid clamp to provide single-stranded template for the allele-specific arrayed primer extension reaction, incorporating cyanine-5-deoxycytidine triphosphate in the newly synthesized strands. The fluorescent product was visualized by laser at 670 nm.
  
  
  RESULTS
  Eleven different types of EGFR TKI drug-sensitive mutants (SM) were identified in plasma-DNA from 46 of 51 patients. Five patients carried only wild-type sequence. Plasma-DNA finding was concordant in 36 of 37 cases with tumor-sequencing data. This method could detect as little as 62.5 copies of mutant L858R; 125 copies of E709K + G719A or 625 copies of del 746-750 in the presence of 100,000 copies of wild-type EGFR. In 21 patients on longitudinal follow-up for up to 18 months, SM was found in all initial plasma samples, except for three samples collected after recent chemotherapy. Nine of 16 patients (56%) who responded to TKI had undetectable plasma EGFR mutant. SM was present concurrently with drug-resistant mutant in 44% of patients with disease progression while on TKI, the remaining 56% might have other mechanisms of resistance.
  
  
  CONCLUSIONS
  The EGFR array provides a sensitive, inexpensive, and robust method for monitoring non-small-cell lung cancer patients' response to TKI, and obviates the need of repeated lung biopsy.
authors.affiliation: University Department of Medicine, Queen Mary Hospital, Pokfulam Road, Hong Kong.
authors.forename: Irene
authors.initials: I
authors.lastname: Yam
authors.forename: David Chi-Leung
authors.initials: DC
authors.lastname: Lam
authors.forename: Kaimin
authors.initials: K
authors.lastname: Chan
authors.forename: James
authors.initials: J
authors.lastname: Chung-Man Ho
authors.forename: Mary
authors.initials: M
authors.lastname: Ip
authors.forename: Wah-Kit
authors.initials: WK
authors.lastname: Lam
authors.forename: Tai-Kwong
authors.initials: TK
authors.lastname: Chan
authors.forename: Vivian
authors.initials: V
authors.lastname: Chan
mesh_terms: D000230:Adenocarcinoma / Q000097:blood / Q000235:genetics / Q000473:pathology; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D014408:Biomarkers, Tumor / Q000097:blood / Q000235:genetics*; D002289:Carcinoma, Non-Small-Cell Lung / Q000097:blood* / Q000235:genetics* / Q000473:pathology; D002294:Carcinoma, Squamous Cell / Q000097:blood / Q000235:genetics / Q000473:pathology; D003430:Cross-Sectional Studies; D004252:DNA Mutational Analysis; D004273:DNA, Neoplasm / Q000097:blood / Q000235:genetics*; D019008:Drug Resistance, Neoplasm / Q000235:genetics; D066246:ErbB Receptors / Q000235:genetics*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008137:Longitudinal Studies; D008175:Lung Neoplasms / Q000097:blood / Q000235:genetics / Q000473:pathology; D008297:Male; D008875:Middle Aged; D009154:Mutation / Q000235:genetics*; D016133:Polymerase Chain Reaction; D011379:Prognosis; D047428:Protein Kinase Inhibitors / Q000627:therapeutic use; D055752:Small Cell Lung Carcinoma / Q000097:blood / Q000235:genetics / Q000473:pathology
chemical_list: D014408:Biomarkers, Tumor; D004273:DNA, Neoplasm; D047428:Protein Kinase Inhibitors; C512478:EGFR protein, human; D066246:ErbB Receptors