Published online before print February 7, 2008

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Journal of Molecular Diagnostics 2008, Vol. 10, No. 2
Copyright © 2008 American Society for Investigative Pathology & Association for Molecular Pathology
DOI: 10.2353/jmoldx.2008.070125

Epidermal Growth Factor Receptor (EGFR) High Gene Copy Number and Activating Mutations in Lung Adenocarcinomas Are Not Consistently Accompanied by Positivity for EGFR Protein by Standard Immunohistochemistry

Ferenc Pinter^*, Judit Papay, Andrea Almasi, Zoltan Sapi, Edit Szabo, Melinda Kanya, Anna Tamasi, Balazs Jori^*, Edit Varkondi, Judit Moldvay, Klara Szondy, Gyorgy Keri^¶, Massimo Dominici^||, Pierfranco Conte^||, Sandor Eckhardt^**, Laszlo Kopper, Richard Schwab^* and Istvan Petak^*

From KPS Medical Biotechnology and Healthcare Services, * Budapest, Hungary; the First Department of Pathology and Experimental Cancer Research and the Department of Pulmonology, Semmelweis University, Budapest, Hungary; Rational Drug Design Laboratories CRC, Budapest, Hungary; Pathobiochemistry Research Group, ^¶ Hungarian Academy of Sciences, Budapest, Hungary; National Institute of Oncology, ** Budapest, Hungary; and the Department of Oncology and Hematology, ^|| University of Modena and Reggio Emilia, Modena, Italy

The purpose of this study was to investigate whether detectable protein biomarker overexpression is a prerequisite for the presence of increased gene copy number or activating mutations and responsiveness to the epidermal growth factor receptor (EGFR) inhibitors gefitinib and erlotinib in patients with lung adenocarcinomas. EGFR status was prospectively analyzed in tumor biopsy samples by three methods: protein expression (n = 117) by standardized immunohistochemistry (IHC), gene copy number (n = 97) by fluorescent in situ hybridization (FISH), and mutation analysis by sequencing (n = 126). Fifty-nine percent of the samples were positive by IHC, 40% were positive by FISH, and 13.5% contained activating kinase domain mutations. Thirty-four percent of the FISH-positive and 27% of the mutant samples were also IHC-negative. All EGFR mutant patients had major clinical responses (five complete response and five partial response) to gefitinib or erlotinib treatment, although three of these tumors were IHC-negative and four were FISH-negative. In a retrospective analysis of samples from nine patients with excellent therapeutic responses (three complete response, five partial response, one stable disease) to erlotinib or gefitinib, mutations were identified in eight cases, but IHC was negative in four of these tumors. These results indicate that molecular diagnostic methods appear to be most important for the identification of lung adenocarcinoma patients who may benefit from EGFR inhibitor treatments.

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