RESUMEN
BACKGROUND AND OBJECTIVE: Breast cancer is the most common malignancy among women. The Neoadjuvant chemotherapy is the treatment of choice for non-operable tumors. The Ki67 is a proliferation marker that can be used to predict the therapeutic response to chemotherapy and the patients' prognosis. METHODS: This retrospective study was carried out on 55 consecutive patients with breast cancer referred to a Training Tertiary Healthcare Center in Kerman, Iran since 2009 to 2014. After diagnostic approval, the tissue samples of patients were examined for estrogen and progesterone receptors, ki67 and HER2-neu markers by using immunohistochemical staining. Then the patients were treated with 6 cycles of Neoadjuvant chemotherapy regimens by Doxorubicin and Taxans or 4 chemotherapy cycles, containing Anthracycline and Cyclophosphamide and 4 cycles of Paclitaxel. After mastectomy, their samples were reexamined for ki67 again and classified into three groups (low: ki67<15%), medium (Ki67 = 16-30%) and high (Ki67> 30%). RESULTS: Before chemotherapy, 54.5% of the patients had high expression of Ki67. But after chemotherapy, 52.7 of the patients had complete therapeutic response showing that the Ki67 level was reduced significantly (P=0.003). CONCLUSION: Before and after Neoadjuvant chemotherapy, Ki67 measurements may be used as a predictive marker of therapeutic response.