Ki67 measured after neoadjuvant chemotherapy for primary breast cancer.

Purpose: The value of Ki67 measured on residual disease after neoadjuvant chemotherapy is not sufficiently described.

Experimental Design: Participants of the GeparTrio study with primary breast cancer randomly received neoadjuvant response-guided [8 cycles TAC (docetaxel/doxorubicin/cyclophosphamide) in responding and TAC-NX (vinorelbine/capecitabine) in nonresponding patients] or conventional (6 cycles TAC) chemotherapy according to interim response assessment. Ki-67 levels were centrally measured immunohistochemically after neoadjuvant treatment if tumor tissue was available.