EGFR Gene Amplification and Protein Expression in Invasive Ductal Carcinoma of the Breast

BACKGROUND: The epidermal growth factor receptor (EGFR) is a surrogate marker for basal-like breast cancer. A recent study suggested that EGFR may be used as a target for breast cancer treatment. METHODS: A total of 706 invasive ductal carcinomas (IDC) of the breast were immunophenotyped, and 82 cases with EGFR protein expression were studied for EGFR gene amplification. RESULTS: EGFR protein was expressed in 121 of 706 IDCs (17.1%); 5.9% were of luminal type, 25.3% of epidermal growth factor receptor 2 (HER-2) type, and 79.3% of basal-like tumors. EGFR gene amplification and high polysomy (fluorescent in situ hybridization [FISH]-positive) were found in 18 of 82 cases (22.0%); 41.2% of the HER-2(+), EGFR(+), cytokeratin 5/6(-) (CK5/6(-)) group, 11.2% of the HER-2(-), EGFR(+), CK5/6(-) group, and 19.1% of the HER-2(-), EGFR(+), CK5/6(+) group. FISH-positive cases were detected in 8.3% of the EGFR protein 1(+) expression cases, 15.9% of 2(+) expression cases, and 38.5% of 3(+) expression cases. In group 2, the tumors had a high Ki-67 labeling (>60%), but the patients showed better disease-free survival than those with tumors that co-expressed HER-2 or CK5/6. CONCLUSIONS: EGFR-directed therapy can be considered in breast cancer patients with EGFR protein overexpression and gene amplification, and its therapeutic implication should be determined in HER-2 type breast cancer patients.