EGFR mutation status in pleural fluid predicts tumor responsiveness and resistance to gefitinib

Junichi Sou, Shinichi Toyooka, Shuji Ichihara, Hiroshi Suehisa, Naruyuki Kobayashi, Sachio Ito, Masaomi Yamane, Motoi Aoe, Yoshifumi Sano, Katsuyuki Kiura, Hiroshi Date

Research output: Contribution to journalArticlepeer-review

26 Citations (Scopus)


It has been reported that the threonine-to-methionine substitution at amino acid position 790 (T790M) of the epidermal growth factor receptor (EGFR) gene is correlated with acquired resistance to gefitinib. We previously reported that there was some population that harbored the EGFR T790M mutation as a minor clone of tumor cells prior to drug treatment, may be causing resistance to gefitinib during treatment. This fact also suggests that the detection of the EGFR T790M mutation prior to treatment may predict the development of resistance. We also showed that pleural fluid is a useful specimen for detection of EGFR mutation using sensitive assays. In this study, we reported a female patient who was treated with gefitinib because an EGFR L858R mutation was found in her pleural fluid. Our patient showed partial response to gefitinib, but she had progressive disease only 4 months after the start of treatment. Furthermore, the EGFR T790M mutation was detected in the pleural fluid before gefitinib treatment by the mutant-enriched PCR assay. Our findings confirmed that the EGFR T790M mutation was occasionally present as a minor population in tumor cells before treatment and caused resistance after gefitinib administration. The detection of a small fraction of T790M-positive alleles may be useful to predict the clinical course of the gefitinib-treated non-small-cell lung cancer patients.

Original languageEnglish
Pages (from-to)445-448
Number of pages4
JournalLung Cancer
Issue number3
Publication statusPublished - Jun 2007


  • EGFR
  • Gefitinib
  • Mutation
  • Pleural effusion
  • Pleural fluid
  • T790M

ASJC Scopus subject areas

  • Oncology
  • Pulmonary and Respiratory Medicine
  • Cancer Research


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