Prognostic value of KI-67 proliferation index in luminal breast cancers

Objective: This study aimed to examine the prognostic significance of the KI-67 proliferation index, especially in breast cancer (BC) patients without HER-2 expression and no nodal involvement.Material and methods: The database of hormone-receptor-positive patients who underwent surgery for BC in our Surgical Oncology Clinic between 2008 and 2020 was retrospectively reviewed and recorded.Patients were categorized based on their KI-67 level, considering the cutoff value of 20%.Results: Our study revealed that tumors with high KI-67 levels were more likely to have a more advanced histological grade (p = 0.00) and size (p = 0.038).In the univariant analysis, KI-67 level was effective on overall survival (p = 0.044) and disease-free survival (p = 0.048).However, we found that there was no independent prognostic factor in the multivariant analysis.Conclusion: Although the Ki-67 proliferation index does not yet have an agreed threshold value and scoring methodology, it can also be used to determine prognosis and evaluate treatment response in some patients.