title: Rare and complex mutations of epidermal growth factor receptor, and efficacy of tyrosine kinase inhibitor in patients with non-small cell lung cancer.
abstract: BACKGROUND
  There are many complex and rare mutations in the epidermal growth factor receptor (EGFR) gene in non-small cell lung cancer (NSCLC) other than the two classical mutations of L858R and exon 19 deletional mutation. The purpose of this study was to investigate the clinical significance of rare and complex mutations, and the efficacy of EGFR tyrosine kinase inhibitors (TKIs).
  
  
  METHODS
  We analyzed 1,431 NSCLC patients who were treated with either gefitinib or erlotinib. Exons 18 to 21 of EGFR were analyzed by PCR and subjected to direct sequencing methods.
  
  
  RESULTS
  Of 306 patients who had EGFR mutation, 24 patients (7.3 %) had complex mutations. The frequency of rare mutations was 10.3 %. Four groups were categorized [group A (N = 269): classical mutation alone; group B (N = 16): complex mutation with classical mutation; group C (N = 16): rare mutation alone or complex mutation with rare mutation; group D (N = 5); classical mutation with T790M]; the response rate (RR) to TKI was significantly different between each group (RR = 74.8 % in group A vs. 68.8 % in group B vs. 25.0 % in group C vs. 80.0 % in group D, P < 0.001). Progression-free survival (PFS) was also poorer in rare mutations (median PFS: 11.9 vs. 8.1 vs. 1.4 vs. 8.0 months, respectively, P < 0.001).
  
  
  CONCLUSIONS
  NSCLC patients harboring rare mutations did not show consistent and favorable responses to EGFR TKI compared with those harboring classical mutations. However, complex mutations with classical mutations showed similar treatment efficacy toward EGFR TKI to that with classical mutations alone.
authors.affiliation: Department of Internal Medicine, Seoul National University Hospital, 101 Daehak-ro, Jongno-gu, Seoul, 110-744, Korea.
authors.forename: Bhumsuk
authors.initials: B
authors.lastname: Keam
authors.forename: Dong-Wan
authors.initials: DW
authors.lastname: Kim
authors.forename: Jin Hyun
authors.initials: JH
authors.lastname: Park
authors.forename: Jeong-Ok
authors.initials: JO
authors.lastname: Lee
authors.forename: Tae Min
authors.initials: TM
authors.lastname: Kim
authors.forename: Se-Hoon
authors.initials: SH
authors.lastname: Lee
authors.forename: Doo Hyun
authors.initials: DH
authors.lastname: Chung
authors.forename: Dae Seog
authors.initials: DS
authors.lastname: Heo
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002289:Carcinoma, Non-Small-Cell Lung / Q000188:drug therapy* / Q000235:genetics* / Q000473:pathology; D018572:Disease-Free Survival; D066246:ErbB Receptors / Q000235:genetics*; D000069347:Erlotinib Hydrochloride; D005260:Female; D000077156:Gefitinib; D006801:Humans; D008297:Male; D008875:Middle Aged; D009154:Mutation; D009367:Neoplasm Staging; D047428:Protein Kinase Inhibitors / Q000008:administration & dosage*; D011799:Quinazolines / Q000008:administration & dosage
chemical_list: D047428:Protein Kinase Inhibitors; D011799:Quinazolines; D000069347:Erlotinib Hydrochloride; D066246:ErbB Receptors; D000077156:Gefitinib
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