Determination of EGFR protein expression by IHC and EGFR gene status by FISH in high-grade gliomas

The Epidermal growth factor receptor (EGFR) plays an important role in cancer pathogenesis and biology with amplification reported in 20-40% of high-grade gliomas. Immunohistochemistry (IHC) and Fluorescence In Situ Hybridization (FISH) tests can determine the expression and amplification status of the EGFR EG gene. Both tests could be usefull for the stratification of patients that are recruited in therapeutic studies with the anti-EGFR targeted agents that have recently become available in the clinic. The aim of the study was to determine the usefulness of IHC and FISH for the expression and amplification status of the EGFR gene in adult high-grade gliomas and to correlate the information that is obtained by both tests. Tumor tissues were collected from a retrospective cohort of 63 adult patients with high-grade glioma. FISH identified amplification of the EGFR gene in 4/17 anaplastic astrocytoma (AA, 26,7%) and 15/46 glioblastoma multiforme (GBM, 31,9%) while a positive IHC staining was observed in 12/17 AA (70,6%) and 39/46 GBM (84,8%). In our experience a positive IHC result did not correlate with EGFR gene amplification status as determined by FISH. Interpretation of the results obtained by EGFR FISH was more straightforward as compared to IHC and therefore we consider this test appropriate for stratification of patients in clinical trials with EGFR targeted agents.