Treatment outcomes of stage IIA–IIB breast cancer patients of hormone-positive HER2-negative subtype after neoadjuvant polychemotherapy depending on Ki-67 levels

Objective. To evaluate clinical and pathological responses to neoadjuvant polychemotherapy (NACT) in patients with stage IIAIIB breast cancer of hormone-positive HER2-negative subtype depending on the level of tumor cell proliferation index (Ki-67), and to analyze the volume of surgical intervention. Material and methods. We analyzed the results of treatment of 100 patients who received NACT according to the 4AC+12P/4T regimen at the first stage of complex treatment followed by surgical treatment in the Department of Oncology and Reconstructive and Plastic Surgery of Breast and Skin of the P.A. Herzen Moscow Medical Oncology Research Institute in the period from 2013 to 2022. On the basis of Ki-67 level the study participants were divided into three groups: the first group with Ki-67 20— 30% included 24 patients, the second group with Ki-67 31—50% — 41 patients, and the third group with Ki-67>50 — 35 patients. Results. In the group with Ki-67 20—30% a complete clinical response (cCR) was achieved in 4 (16.7%), whereas a complete pathological response (pCR) was confirmed only in 1 (4.2%); with Ki-67 in the range 31—50% cCR and pCR were the same and were noted in 4 (9.8%); with Ki-67>50% cCR was recorded in 9 (25.7%), p-CR in 8 (22.9%) patients. There were no significant differences between groups in the incidence of cCR (p=0.181; adjusted p=0.545) as well as pCR (p=0.081; adjusted p=0.321). In the general population, the cCR (ycT0N0) rate was 17% and the pCR (ypT0-isN0) rate was 13%. Breast-conserving surgeries were performed in 40% and mastectomies in 60% of cases. Conclusion. This study demonstrated low cCR and pCR rates in the general population of patients with hormone-positive HER2negative subtype of cancer, as well as no differences in the frequency of their achievement between groups with different Ki-67 levels. The rate of organ-preserving surgeries performed was lower compared with mastectomies. © 2025 Elsevier B.V., All rights reserved.