Prognostic value of immunophenotypic classification of breast cancer in high-risk patients treated with dose-dense sequential adjuvant chemotherapy.

e21110 Background: It is well recognized that breast cancer is a heterogeneous disease that is composed of several molecular subtypes with substantial differences in growth rate, invasiveness and treatment response. Estrogen receptors (ER), progesterone receptors (PgR) and HER2 are important determinants of these molecular subtypes, since they drive specific targeted treatments, such as antiestrogens, aromatase inhibitors and trastuzumab. Methods: 595 patients with high-risk breast cancer were treated with adjuvant anthracycline-based dose-dense sequential chemotherapy with or without paclitaxel (E-T-CMF vs. E-CMF) in the context of a randomized Phase III study. ER, PgR, HER2, Ki67, EGFR, and CK5 were evaluated in 298 formalin-fixed tumor samples by immunohistochemistry (IHC). HER2 was also evaluated by chromogen in situ hybridization (CISH) using ZYMED (InVitrogen) technology and was used to determine HER2 status for patients that had a score different than +3 by IHC. Identification of the immunophenotyp...