Comparison between epidermal growth factor receptor (EGFR) gene in primary non-small cell lung cancer (NSCLC) and in fine needle aspirates from metastatic sites

Abstract

21081 Background: Epidermal growth factor receptor (EGFR) gene copy number obtained by fluorescence in situ hybridization (FISH) has been recently proposed to predict which non-small cell lung cancer patients (NSCLC) are expected to benefit from EGFR tyrosine kinase inhibitors. However, it is still unknown whether EGFR status differs in metastases compared to primary NSCLC. In all studies, FISH have been performed on histological material. The possibility to perform FISH analysis on cytological material obtained by fine-needle aspiration from superficial and deep metastases would allow to know the real EGFR status when the metastatic site is not accessible for biopsy. Methods: EGFR gene copy number was analyzed by FISH on fine-needle aspirates (FNAs) obtained from 18 patients with metastatic NSCLC (11 lymphnod, 2 liver, 1 abdomen, 2 skin, 2 pleural effusion) and results were compared with those obtained on corresponding paraffin histological sections from the primary tumor. Results: The feasibility of EGFR-FISH on cytology was 89%; 2/18 samples were not evaluable because of lack of hybridization. EGFR-FISH was positive (= 4 EGFR copy number; Cappuzzo F. et al, JNCI 2005) in 69% (11/16) of the metastases and in 38% (6/16) of the primary tumors. Five of the 16 cases were EGFR positive on both primary tumor and metastatic site and 4 were negative on both primary tumor and metastasis. Seven cases (44%) showed primary tumor vs. metastasis discordance: in 6 cases EGFR was positive in the metastatic site but not in the primary tumor, while in one sample EGFR was positive in the primary tumor but not in the metastasis. Conclusions: EGFR-FISH can be reliably assessed on FNAs obtained from NSCLC metastases. Possible changes in EGFR status during the metastatic progression as well as cancer heterogeneity may account for discrepancies observed between primary tumor and metastatic sites. These findings should be considered in future studies which will be design to better elucidate the predictive role of EGFR-FISH in NSCLC. No significant financial relationships to disclose.