New insights into the prognostic value of Ki 67 labeling index in patients with triple negative breast cancer
The clinicopathological importance of the Ki 67 labeling index (LI) in breast cancer has been studied intensely; however, its prognostic significance in triple negative breast cancer (TNBC) is unclear. We aimed to determine the optimal Ki 67 cut off point to demonstrate its prognostic relevance for breast cancer specific survival (BCSS) in TNBC patients. A total of 571 female TNBC patients underwent diagnosis and surgery at our institution from January 2002 to June 2011. Clinicopathological information for all patients was available and categorized by Ki 67 LI and age at diagnosis. The cut off values for Ki 67 LI and age were selected using the medians. A varying coefficient Cox model was used to describe the effect of Ki 67 LI on BCSS outcomes changing with age after adjustment for disease characteristics. For survival analysis, the Kaplan Meier method and the log rank test were used. Cox proportional hazards models were applied to determine the association of Ki 67 LI and age with BCSS outcomes after adjustment for disease characteristics. Median age was 50 years, and median Ki 67 LI was 35% (range, 0 97.5% There was no prognostic significance of stratification by Ki 67 LI in all patients. When analyzing age at diagnosis as a continuous variable, the log transformed HRKi67 35% vs. 35% for BCSS increased in an S shaped curve with increasing age up to about 50 years old and remained higher risk for high Ki 67 LI. After adjusting for clinicopathological risk factors, low Ki 67 LI was a poor prognostic factor for BCSS (HR: 0.36, 95% CI: 0.14 0.96, P 0.042) in patients of 50 years, but not in patients diagnosed at 50 years (hazard ratio [HR] 1.57, 95% CI: 0.76 3.22, P 0.241) In conclusion, lower Ki 67 LI has poor prognosis relevance in TNBC patients diagnosed at 50 years old. Further validation of the clinical significance of Ki 67 LI in TNBC is required.
Oncotarget