Association between Ki‑67 expression and clinicopathological features in prognosis of breast cancer: A retrospective cohort study

Background: Breast cancer is the most common diagnosed female cancer. Breast cancer is also the leading cause of cancer death in females accounting for 13.7% of female cancer‑related mortality globally. Variable known prognostic factors such as histological tumor type, tumor size, nodal status, grade, age, and estrogen receptor (ER) status and the proliferation marker – Ki‑67 influence the type of treatment decision. The purpose of this present study is to investigate the association between Ki‑67 expression with several clinicopathological variables and patients’ outcome. Materials and Methods: This is a retrospective cohort study from September 2008 to March 2017; 165 newly diagnosed breast cancer patients were enrolled in the study. Ki67 levels were measured using immunohistochemistry and compared with clinicopathological variables. The relation of Ki67 expression with disease‑free survival (DFS) and overall survival (OS) was also analyzed. Results: The result of this study revealed that age, tumor size, menopausal status, and human epidermal growth factor receptor 2 (HER2) status had no effect on the patients’ outcome. Patients with ER‑positive, progesterone receptor (PR)‑positive, and HER2‑negative tumors expressed a higher rate of Ki‑67 (>10%) than patients with ER‑negative, PR‑negative, and HER2‑positive tumors, respectively. However, we found that Ki‑67 levels were not significantly increased statistically with ER, PR, and HER2 statuses. There was a statistically significant correlation between Ki‑67 expression and with higher stages of the disease. Multivariate analysis showed that Ki‑67 expression could not to be an independent prognostic factor for 5‑year OS and DFS. Furthermore, p53 status was only prognostic factor for 5‑year OS whereas higher stages of disease and p53 status were prognostic factors for 5‑year DFS. Conclusion: Ki67 could not be an independent variable for prediction of breast cancer outcome.