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Open Access Highly Accessed Research article

Correlations of EGFR mutations and increases in EGFR and HER2 copy number to gefitinib response in a retrospective analysis of lung cancer patients

Trevor J Pugh1, Gwyn Bebb2, Lorena Barclay3, Margaret Sutcliffe3, John Fee3, Chris Salski4, Robert O'Connor4, Cheryl Ho5, Nevin Murray5, Barbara Melosky5, John English6, Jeurgen Vielkind3, Doug Horsman4, Janessa J Laskin5 and Marco A Marra1*

  • * Corresponding author: Marco A Marra mmarra@bcgsc.ca

  • † Equal contributors

Author Affiliations

1 Michael Smith Genome Sciences Centre, BC Cancer Agency, Vancouver, Canada

2 Tom Baker Cancer Centre, Calgary, BC, Canada

3 Department of Cancer Endocrinology, BC Cancer Agency, Vancouver, Canada

4 Department of Pathology, BC Cancer Agency, Vancouver, Canada

5 Department of Medical Oncology, BC Cancer Agency, Vancouver, Canada

6 Department of Pathology and Laboratory Medicine, Vancouver Hospital, Vancouver, Canada

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BMC Cancer 2007, 7:128  doi:10.1186/1471-2407-7-128

Published: 13 July 2007

Abstract

Background

Gefitinib, a small molecule tyrosine kinase inhibitor of the Epidermal Growth Factor Receptor (EGFR), has shown limited efficacy in the treatment of lung cancer. Recognized clinical predictors of response to this drug, specifically female, non-smoker, Asian descent, and adenocarcinoma, together suggest a genetic basis for drug response. Recent studies have addressed the relationship between response and either sequence mutations or increased copy number of specific receptor tyrosine kinases. We set out to examine the relationship between response and the molecular status of two such kinases, EGFR and HER2, in 39 patients treated with gefitinib at the BC Cancer Agency.

Methods

Archival patient material was reviewed by a pathologist and malignant cells were selectively isolated by laser microdissection or manual recovery of cells from microscope slides. Genomic DNA was extracted from 37 such patient samples and exons 18–24, coding for the tyrosine kinase domain of EGFR, were amplified by PCR and sequenced. EGFR and HER2 copy number status were also assessed using FISH in 26 samples. Correlations between molecular features and drug response were assessed using the two-sided Fisher's exact test.

Results

Mutations previously correlated with response were detected in five tumours, four with exon 19 deletions and one with an exon 21 missense L858R point mutation. Increased gene copy number was observed in thirteen tumours, seven with EGFR amplification, three with HER2 amplification, and three with amplification of both genes. In our study cohort, a correlation was not observed between response and EGFR mutations (exon 19 deletion p = 0.0889, we observed a single exon 21 mutation in a non-responder) or increases in EGFR or HER2 copy number (p = 0.552 and 0.437, respectively).

Conclusion

Neither mutation of EGFR nor increased copy number of EGFR or HER2 was diagnostic of response to gefitinib in this cohort. However, validation of these features in a larger sample set is appropriate. Identification of additional predictive biomarkers beyond EGFR status may be necessary to accurately predict treatment outcome.