Abstract 2396: High EGFR gene copy number predicts poor outcome in triple-negative breast cancer.

Abstract

Abstract INTRODUCTION: Epidermal growth factor receptor (EGFR) is frequently expressed in triple-negative breast cancer and is emerging as a new therapeutic target. However, the rate of EGFR gene copy number alteration and mutation has been reported to be quite variable and their prognostic significance is poorly defined in triple-negative breast cancer. METHOD: We examined EGFR protein expression, gene copy number alteration and mutation in 150 cases of tripe-negative breast cancer and correlated their findings with clinical outcome of the patients. EGFR protein expression was evaluated by immunohistochemistry using whole tissue sections and EGFR copy number alteration was assessed by dual-color fluorescence in situ hybridization using tissue microarrays. EGFR mutation analysis was performed by polymerase chain reaction of exon 18 to 21 of EGFR gene and direct sequencing of PCR products. RESULT: EGFR protein was expressed in 117 of 150 cases (78.0%). High EGFR gene copy number was found in 33.3% of the cases (amplification in 2.0% and high polysomy in 31.3%). Five EGFR mutations were detected in 4 of 150 cases (2.7%) with G719A in exon 18 (n=1), V786M in exon 20 (n=1) and L858R in exon 21 (n=3). One case had two mutations (G719A and L858R). High EGFR copy number, but not EGFR mutation, was correlated with EGFR protein over-expression. In survival analyses, high EGFR copy number gain was found to be a poor prognostic factor for relapse-free survival (p=0.046), especially for metastasis-free survival (p=0.016). CONCLUSION: EGFR mutation is found to be a rare event in triple-negative breast cancer. However, high EGFR copy number is relatively frequent and is associated with poor clinical outcome in triple-negative breast cancer, suggesting that evaluation of EGFR gene copy number is beneficial for the prediction of outcome in patients with triple-negative breast cancer and selection of the patients for anti-EGFR targeted therapy. Citation Format: Heae Surng Park, Min Hye Jang, Eun Joo Kim, Hyun Jeong Kim, Hee Jin Lee, So Yeon Park. High EGFR gene copy number predicts poor outcome in triple-negative breast cancer. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2396. doi:10.1158/1538-7445.AM2013-2396