Abstract: Background and purpose: Breast cancer is one of the most common malignancies in women. Endocrine therapy is one of the most important therapeutics in breast cancer systemic therapy. However, about 30% of hormone-sensitive breast cancer patients do not benefit from endocrine therapy. The expression of fibroblast growth factor receptor 1 (FGFR1) may be involved in endocrine therapy resistance in estrogen receptor (ER)-positive breast cancer patients. FGFR1 is widely recognized for playing key roles in mammary carcinogenesis and further affecting the prognosis and therapeutic response of breast cancer. The aim of this study was to investigate the effect of FGFR1 protein expression on the clinicopathological features and prognosis of ERpositive breast cancer. Methods: One hundred and eighty-four ER-positive breast cancer cases treated in Harbin Medical University Cancer Hospital from September 2008 to December 2011 were studied, and their FGFR1 protein expressions were measured by the immunohistochemistry method. Pearson’s chi-square test was utilized to analyze the association between FGFR1 expression and disease characteristics. COX regression and Kaplan-Meier analyses were performed to evaluate the effect of FGFR1 on the prognosis of ER-positive breast cancer. Results: The results showed that patients with higher FGFR1 expression were more likely to have lymph node metastasis (P=0.012, r=0.186), and their ER levels were negatively associated with FGFR1 expression (P=0.011, r=-0.221). In univariate COX regression analyses, TNM stage, regional lymph node metastasis status, Ki-67 positive rate and FGFR1 expression were correlated with the prognosis of ER-positive breast cancer. It was found by multiple factors analysis of data that lymph node metastasis status (OR=1.744, 95%CI: 1.002-3.034, P=0.049) and Ki-67 positive rate (OR=1.882, 95%CI: 1.015-3.491, P=0.045) were independent prognostic factors for ER-positive breast cancer. Kaplan-Meier analysis showed that high indicate FGFR1 expression was correlated with decreased overall survival (P=0.036). Conclusion: There was a significant negative correlation between FGFR1 expression and ER level in ER-positive breast cancer, and high FGFR1 protein level was associated with a poor prognosis.

Key words: Breast cancer, Fibroblast growth factor receptor 1, Estrogen receptor-positive, Immunohistochemistry, Prognosis