ABSTRACT
BACKGROUND: Since the anti-HER2 monoclonal antibody trastuzumab made its triumphant advance into breast cancer therapy, new selective agents, including pan-HER inhibitors are entering clinical practice. MATERIALS AND METHODS: This study investigates the expression of the four HER-family members, HER1-4, in 48 primary breast carcinomas (PBC) and corresponding distant metastases (CDM) by immunohistochemistry and fluorescence in situ hybridisation. RESULTS: Concordance rate between PBC and CDM was 79% for HERI and HER2, 67% for HER3 and 56% or HER4. Expression of HER1-3 was associated with poor prognosis compared to HER-negative disease (p = 0.036). HER4 overexpression was associated with a better outcome (p = 0.003). CONCLUSION: Though most tumours demonstrate a stable HER expression pattern, both loss and acquisition of HER receptor overexpression can occur during metastasis. HER4 overexpression predicts prolonged survival compared to receptor negative disease, while the opposite is true for HER1-3. Consequences for modem antibody therapy are discussed.
