Background: Recently, it was found that the overexpression and mutation status of EZH2 affect cancer progression and patient outcome in several human tumors. We aimed to evaluate the clinicopathologic significance of EZH2 in patients with breast cancer.
Methods: This was an analytical descriptive study of surgical specimens of primary breast tumors. Specimens were analyzed immunohistochemically for EZH2, estrogen receptor, progesterone receptor, Ki-67, P53, and human epidermal growth factor receptor 2 (HER2) expressions. Regression analysis was performed to calculate hazard ratios (HRs) and 95% CIs. Kaplan-Meier and Cox regression models were used to estimate the overall survival (OS) and disease-free survival (DFS).
Results: We included 100 patients with breast cancer (mean age 51.05±9.54 years). The multivariate regression analysis showed that HER2-positive patients had approximately twice the levels of EZH2 expression compared with HER2-negative patients (HR 2.16, 95% CI 0.48-11.49). The likelihood of EZH2 expression was significantly higher in patients with lymph node involvement than in those without (HR 8.44, 95% CI 3.06-23.33; P≤0.05). EZH2 expression did not have any significant effect on the OS, although the mean OS in high EZH2 expression was shorter than for those with low EZH2 expression (655 vs 787 days; log-rank P=0.336). The mean DFS was 487 days for patients with high EZH2 expression compared with 908 days for those with low EZH2 expression (log-rank P=0.188).
Conclusion: There was no association found between EZH2 expression and OS and DFS in our patients. Further studies involving larger sample sizes, and conducted in different populations, are needed to validate this hypothesis.
Keywords: breast cancer; enhancer of zeste homolog 2 protein; survival analysis; tumor markers.