Factors Predicting Response in Breast Cancer Receiving Neoadjuvant Therapy and the Role of Ki67 Labeling Index

To determine the predictive value of Ki67 on pathological complete response (pCR) of breast and axilla regions in breast cancer (BC) patients receiving neoadjuvant therapy (NAT).Descriptive study. Place and Duration of the Study: Departments of Medical Oncology, Sirnak State Hospital, Aydin State Hospital, Manisa Celal Bayar University, and Dokuz Eylul University, from November 2010 to July 2022.PCR and various histopathological parameters were evaluated for BC patients receiving NAT. The Youden Index method was used to find the cut-off value for the Ki67 variable according to the receiver operating characteristic (ROC) curve. This value was obtained as 77.5. Breast and axillary responses were individually evaluated to assess response to NAT. Univariate and multivariate logistic regression analysis were used to predict both breast and axillary pCR.A total number of 280 females receiving NAT for BC were included in the study. Multivariate analysis for breast pCR to NAT showed that Ki67 index (>77.5 vs <77.5, p=0.047) was statistically significant marker. While Ki67 index was significant for breast pCR in both univariate and multivariate analyses, the same was not observed on axillary response (p=0.387).High Ki67 level was significantly associated with breast pCR in BC patients receiving NAT, but a similar effect was not observed on axillary pCR. These findings suggest that breast and axilla tissues have a biological differences in treatment responses.Axillary response, Breast cancer, Ki67 Labeling Index, Neoadjuvant therapy, pathological complete response.