Importance of Ki-67 in human epidermal growth factor receptor 2 positive breast cancer.

PURPOSE The aim of this study was to evaluate the importance of Ki-67 in Human Epidermal Growth Factor Receptor 2 (Her-2) positive breast cancer patients. METHODS We reviewed the records of patients diagnosed with Her-2-positive non-metastatic breast cancer between 2005 and 2011. Paraffin-embedded tissue samples were stained with MIB-1 mouse monoclonal antibody to find Ki-67 levels. Patients were grouped as low Ki-67<20% and high Ki-67≥20%. Demographic and clinical features were compared. RESULTS One hundred and six patients were included in the study. Median follow up time was 41 months (range 15-100). Median age was 49.5 years (range 29-79). Twenty-nine patients (27.4%) were in the Ki-67 low group. Demographic features were similar in both groups. Lymphovas cular invasion was more frequent in the Ki-67 high group, and hormone receptor (HR) positivity was more frequent in the Ki-67 low group (p=0.03, p=0.03, respectively). Recurrence rate was not significantly different in both groups (p=0.36). T stage (p=0.02), stage (p<0.01), lymphovascular invasion (p=0.02), ER status (p=0.02), and HR status (p<0.01) were related with recurrence. In multivariate analysis, stage and HR negativity were independent factors for recurrence (p<0.01, p=0.01, respectively). Recurrence sites were also similar in both groups. Survival rates at the third year for Ki-67 low group and Ki-67 high group were 94% and 92%, respectively. CONCLUSION Her-2 positive patients with low Ki-67 and high Ki-67 had similar demographic and pathologic features except lymphovascular invasion and HR status. HR status was an important factor for disease course. Clinical course was determined by HR status rather than Ki-67.