Over the past decades, breast cancer (BC) is the most common cancer and one of the key causes of mortality and disability among women in developed countries. Aim: Determination of the role of Ki-67 index in assessing the quality of neoadjuvant polychemotherapy treatment using regional or systemic delivery routes of pharmacological agents in patients with locally advanced breast cancer (LABC). The retrospective analysis of 30 clinical trials of LABC treatment based on selective intra-arterial therapy in patients with BC (T4A-DN0-3M0) was used. The decrease in Ki-67 level in LABC after selective intra-arterial polychemotherapy was more pronounced than after systemic polychemotherapy. No correlation of the tumor metastatic potential with a Ki-67 level was detected. Assessment of Ki-67 expression allows to evaluate effectively the biological properties of the tumor, predict the course of the disease and choose the optimal tactics of neoadjuvant polychemotherapy (regional or systemic variant) as part of integrated antitumor treatment
