Objective: To observe the efficacy and safety of trastuzumab combined with chemotherapy in patients with human epidermal growth factor receptor 2(HER2)-overexpressing advanced breast cancer.Methods: A total of 90 patients with HER2-overexpressing advanced breast cancer were enrolled in this study. All patients were diagnosed with ductal invasive breast cancer by pathological analysis, and were aged between 31–73 years with a median of 51 years. HER2-positivity was defined as 3(+) staining in immunochemistry or amplification of fluorescence in situ hybridization(FISH, ratio ≥2.0). Trastuzumab was administered in combination with chemotherapy as first-line treatment and beyond progression as a secondline, third-line, and above treatment in 90, 34, 14, and 6 patients, respectively. The chemotherapy regimen was given according to normal clinical practice. The response rate was evaluated every two cycles, and the primary endpoints were progression-free survival(PFS) and overall survival(OS). Survival curves were estimated by using Kaplan-Meier graphs and were compared by using log-rank test statistics. Multivariate analysis was done using Cox’s proportional hazards regression model, and the level of significance was P<0.05.Results: All 90 patients received at least one dose of trastuzumab, and efficacy could be evaluated in 85 patients. The median follow-up was 50 months. In total, 72(80.00%) patients had visceral metastasis, and 43(47.78%) patients had progressed after one or more extensive chemotherapy regimens for metastatic diseases. The median PFS for first-line trastuzumab was 10 months(range, 2–59 months), and the median OS after metastasis or initially local advanced disease was 22 months(range, 2–116 months).Conclusions: Trastuzumab combined with chemotherapy was active and well-tolerated as a first-line treatment and even beyond progression in HER2-overexpressing advanced breast cancer as a second-line or third-line treatment. However, its efficacy is certainly less beyond this point. Objective: To observe the efficacy and safety of trastuzumab combined with chemotherapy in patients with human epidermal growth factor receptor 2 (HER2) -overexpressing advanced breast cancer. Methods: A total of 90 patients with HER2-overexpressing advanced breast cancer were enrolled in this study All patients were diagnosed with ductal invasive breast cancer by pathological analysis, and were for ages between 31-73 years with a median of 51 years. HER2-positivity was defined as 3 (+) staining in immunochemistry or amplification of fluorescence in situ hybridization ( FISH, ratio ≥2.0). Trastuzumab was administered in combination with chemotherapy as first-line treatment and beyond progression as a second line, third-line, and above treatment in 90, 34, 14, and 6 patients, respectively. The chemotherapy regimen was given according to normal clinical practice. The response rate was evaluated every two cycles, and the primary endpoints were progression-free survival (PFS) and overall survival (OS). Survival curves were estimated by using Kaplan-Meier graphs and were compared by using log-rank test statistics. Multivariate analysis was done using Cox’s proportional hazards regression model, and the level of significance was P <0.05. Results: All 90 Patients received at least one dose of trastuzumab, and efficacy could be evaluated in 85 patients. The median follow-up was 50 months. In total, 72 (80.00%) patients had visceral metastasis, and 43 (47.78%) patients had progressed after One or more extensive chemotherapy regimens for metastatic diseases. The median PFS for first-line trastuzumab was 10 months (range, 2-59 months), and the median OS after metastasis or initially local advanced disease was 22 months (range, 2-116 months) .Conclusions: Trastuzumab combined with chemotherapy was active and well-tolerated as a first-line treatment and even beyond progression in HER2-overexpressing advanced breast cancer as a second-line or third-line treatment. However, its efficacy is c ertainlyless beyond this point.