A Retrospective Analysis of Ki-67 Index and its Prognostic Significance in Over 800 Primary Breast Cancer Cases

The Ki-67 index is chiefly important for distinguishing between luminal A and luminal B human epidermal growth factor receptor 2 (HER2neu)-negative breast cancer subtypes. However, its ability to predict response to chemotherapy is uncertain.Patients treated for primary breast cancer at the University Hospital of Cologne were identified. Immunohistochemistry for Ki-67 detection was performed according to standard protocols. Kaplan-Meier survival curves were calculated and compared using the log-rank test.Patients with low Ki-67 index had a significantly better disease-free-survival (DFS) than patients with high Ki-67 index (hazard ratio=2.85; 95% confidence interval=1.45-5.59; p=0.002). A significant influence on DFS was demonstrated (hazard ratio(HR)=1.02; confidence interval(CI)=1.00-1.04; p=0.048) within the subgroup of hormone receptor-positive and HER2neu-negative patients, but not within the subgroup of those with luminal B/HER2neu-negative tumors (DFS: p=0.801; overall-survival: p=0.379).The Ki-67 index has a prognostic impact on DFS in patients with hormone receptor-positive and HER2neu-negative tumors. The strict cut-off value was not suitable for distinguishing between high- and low-risk patients and their response to adjuvant chemotherapy.