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


CONCLUSIONS
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.
Pugh
Trevor J
TJ
Michael Smith Genome Sciences Centre, BC Cancer Agency, Vancouver, Canada. tpugh@bcgsc.ca <tpugh@bcgsc.ca>
Bebb
Gwyn
G
Barclay
Lorena
L
Sutcliffe
Margaret
M
Fee
John
J
Salski
Chris
C
O'Connor
Robert
R
Ho
Cheryl
C
Murray
Nevin
N
Melosky
Barbara
B
English
John
J
Vielkind
Jeurgen
J
Horsman
Doug
D
Laskin
Janessa J
JJ
Marra
Marco A
MA
D000970:Antineoplastic Agents / Q000494:pharmacology; D001483:Base Sequence; D002289:Carcinoma, Non-Small-Cell Lung / Q000188:drug therapy* / Q000473:pathology; D015331:Cohort Studies; D004273:DNA, Neoplasm / Q000032:analysis / Q000302:isolation & purification; D066246:ErbB Receptors / Q000235:genetics*; D005260:Female; D000077156:Gefitinib; D018628:Gene Dosage / Q000187:drug effects*; D018734:Genes, erbB-2; D006801:Humans; D008175:Lung Neoplasms / Q000188:drug therapy* / Q000473:pathology; D008297:Male; D008969:Molecular Sequence Data; D009154:Mutation; D020641:Polymorphism, Single Nucleotide; D017434:Protein Structure, Tertiary / Q000235:genetics; D011799:Quinazolines / Q000494:pharmacology* / Q000627:therapeutic use*; D012189:Retrospective Studies; D017422:Sequence Analysis, DNA
D000970:Antineoplastic Agents; D004273:DNA, Neoplasm; D011799:Quinazolines; D066246:ErbB Receptors; D000077156:Gefitinib