Abstract: Background and purpose: Breast cancer is one of the most serious malignant tumors that threaten women’s life. The incidence of breast cancer and the difference of HER-2 gene expression among Chinese Han and other ethnic minorities have become the focus of scholars’ attention. This study aimed to analyze the ethnic differences of HER-2 gene expression in breast cancer in Guizhou province, to evaluate the clinical efficacy of trastuzumab molecular-targeted therapy and to explore the influence of various clinical factors on the prognosis of patients with breast cancer in Guizhou province. Methods: In the study, we retrospectively analyzed the clinical data of 720 patients with breast cancer who were treated in the Cancer Hospital of Guizhou Medical University from Jan. 2007 to Dec. 2013. The Kaplan-Meier method in SPSS 17.0 was used to study the survival analysis including disease-free survival (DFS) and overall survival (OS). Then the log-rank test was used to compare groups. Cox regression model was used to analyze the independent prognostic factors of breast cancer. Results: There were 520 cases (72.2%) with HER-2 negative expression and 200 cases (27.8%) with positive expression in the group of 720 patients. Among 200 HER-2-positive breast cancer patients, 177 patients (177/645, 27.4%) were the Han ethnicity and 23 patients (23/75, 30.7%) are the ethnic minorities. Then 37 patients were treated by anti-HER-2 therapy (18.5%) and 163 were not treated (81.5%) of the 200 HER-2-positive breast cancer patients who were divided into treatment group and control group. According to statistical analysis, the differences in DFS and OS between the treatment group and the control group were significant (P=0.041, P=0.022). Cox regression model showed that estrogen receptor (ER) and Ki-67 were independent prognostic factors in patients with breast cancer (P=0.03, P=0.016), but progesterone receptor (PR) and HER-2 were not independent prognostic factors (P>0.05). Among them, ER and Ki-67 were independent prognostic factors in the Han ethnicity (P=0.018, P=0.031), while PR and HER-2 were not (P>0.05). In the ethnic minorities, ER, PR, HER-2 and Ki-67 were not independent prognostic factors (P>0.05). Conclusion: HER-2 gene positive expression does not have ethnic difference. Treatment with trastuzumab as anti-HER-2 therapy improves prognosis and prolongs DFS and OS in HER-2-positive patients. However, there are less than 20% patients receiving anti-HER-2 treatment in Guizhou Province currently. In this study, we can see that ER or Ki-67 as a prognostic factor for breast cancer has a trend of ethnic difference.

Key words: Breast cancer, HER-2 expression, Targeted molecular therapy, Prognostic factors