Clinicopathological and prognostic significance of Ki-67 immunohistochemical expression of distant metastatic lesions in patients with metastatic breast cancer.

Background: Surgical biopsy of metastatic lesions followed by pathological confirmation for the investigation of biomarkers is occasionally proposed as an effective strategy in the treatment of metastatic breast cancer. However, few reports have examined Ki-67 immunohistochemical expression in distant metastatic lesions of breast cancer patients. This study aimed to investigate the clinicopathological significance of subtypes and Ki-67 immunohistochemical expression in metastatic breast cancer lesions.
Methods: We retrospectively studied surgical specimens of primary breast cancer tumors and their corresponding metastatic lesions from patients (n = 68) who underwent surgery for primary breast cancer tumors between December 1977 and March 2013. Tissue microarrays were constructed using primary and metastatic lesions, and were stained with antibodies against estrogen receptor, progesterone receptor, human epidermal growth factor receptor 2, and Ki-67. We also examined the clinicopathological characteristics and outcome measures of patients with metastatic breast cancer using primary and paired metastatic lesions.
Results: Compared with the primary lesions, there was no significant difference in subtypes in the metastatic lesions according to metastatic sites. Metastatic lesions of the brain, viscera, and bone exhibited slightly higher levels of Ki-67 immunohistochemical expression compared with primary lesions. A Cox proportional hazards model using multivariate analysis demonstrated that high Ki-67 immunohistochemical expression in distant metastatic lesions was associated with poorer overall survival outcomes after biopsy of recurrence lesion (hazard ratio 2.307; 95% confidence interval 1.207-4.407, P = 0.011).
Conclusions: High Ki-67 immunohistochemical expression levels in distant metastatic lesions were independently associated with poorer overall survival outcomes after biopsy of recurrence lesion in breast cancer patients.