Prognostic Significance of the Ki67 Proliferation Index in Patients with Breast Cancer Using 14% as the Cut-off Value

Aims and background: Reference interval for Ki67 proliferation index, in breast cancer patients is still not determined. Therefore, the aim of this study was to evaluate prognostic value of Ki67 proliferation index in patients with invasive ductal carcinoma of the breast using 14% as the cut-off value. Methods: Correlation of the patient’s age, tumor size, tumor grade, nuclear grade, vascular invasion, axillary node status, estrogen receptor (ER)/ progesterone receptor (PR)/ human epidermal growth factor receptor 2 (HER2) status with Ki67 proliferation index was evaluated. We also analyzed survival outcomes according to Ki67 proliferative index.Results: Ki67 proliferation index ≤14% was significantly associated with patient age >50 years (p<0.001), T1 (p<0.001) and T2 (p<0.002) tumors,negative axillary lymph nodes status (p<0.002), steroid hormone receptor positive tumors (p<0.001), absent vascular invasion (p<0.001), HER2 negative tumors (p<0.001), nuclear grade I (p<0.001) and nuclear grade II (p<0.015) tumors. This study found no correlation between the Ki67 proliferation index ≤14% and the tumor histological grade (p=0.251). Ki67 proliferation index>14% was significantly associated only with T1 tumors (p=0.036). Ki67 proliferation index did not have significant impact on survival(p=0.958).Conclusion: 14% cut-off value for Ki67 proliferation index is not predicting survival in patients with invasive ductal carcinoma of the breast.