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.