OBJECTIVE: To evaluate the efficacy and safety of aromatase inhibitors in the treatment of advanced breast cancer. METHODS: Fifty-two patients with advanced breast cancer treated from June 2003 to September 2006, all women, age range 37 to 75 years, median age 58 years, were observed. Six of the eight premenopausal patients had ovariectomy and two were treated with goserelin to suppress ovarian function. All patients had observable lesions and were treated with aromatase inhibitors for at least 24 weeks, except for 11 cases due to rapid progression of the disease, and the aromatase inhibitors used were exemestane (36 cases), anastrozole (13 cases), and letrozole (3 cases); the main observation indicators were: objective response rate (ORR=CR+PR, where CR is complete remission and PR is partial remission), clinical benefit rate ( CBR=CR+PR+SD≥24 weeks, where SD is disease stabilization), time to tumor progression (TTP), time to tumor treatment failure (TTF), safety and toxic side effects. Results: 6 cases of CR (11.5%), 1 case maintained CR for 152 weeks, 1 case maintained for 96 weeks, and another 4 cases also >60 weeks; 19 cases of PR (36.5%), maintained PR for 32-96 weeks; 16 patients (30.8%) had SD ≥24 weeks; 11 cases (21.2%) had PD (disease progression) + SD <24 weeks. The ORR of patients was 48%, CBR was 78.8%, and mean TTP time was 78.87 weeks (95% CI 61.13%-96.61%). Kap lan2Meier survival curves showed that although patients who did not achieve an objective response had chemotherapy, radiotherapy, or other treatments after disease progression (group B), the survival time was statistically significant compared with patients who achieved an objective response (group A). The difference was statistically significant, with an overall survival rate of 92% in group A and 81.5% in group B at >24 weeks of follow-up [Log Rank (Mantel2Cox) test, χ2 =3.85,P= 0.047]. Drug-related side effects included flushing, sweating, and small joint pain, with two cases of heart failure of uncertain relationship to the treatment drug, which improved with symptomatic treatment. CONCLUSION: Aromatase inhibitor therapy for advanced breast cancer has a single-agent efficiency of 48% ,significantly prolonging the survival of patients who reach CR or PR, with easily tolerated side effects.