Objective：To explore the effect of sequential endocrine therapy in breast cancer patients whose expression of ER and PR was negative preoperatively and was converted to positive by neoadjuvant chemotherapy (NAC).
Methods：The clinical study was carried out in 97 cases of breast cancer whose ER and PR statue were converted from negative to positive after NAC. after NAC the 97 cases were divided into sequential endocrine therapy group and control group. The sequential endocrine group was treated with TAM 10mg Bid for 5 years, the control group was treated with placebo. 
Results： In sequential endocrine treatment group, the 3-and 5-year disease-free survival was 74.5%(38/51) and 60.7%(31/51)  respectively, and the 3-and 5-year overall survival was 80%(41/51) and 74.5%(38/51)  respectively. In control group, the 3-and 5-year disease-free survival was respectively 52.2%(24/46) and 39.1%(18/46), and the 3-and 5-year overall survival was respectively 60.9%(28/46) and 50.0%(23/46). The corresponding values were significantly higher in sequential endocrine therapy group than in control group.
Conclusions： The disease-free and overall survival are significantly increased by applying sequential endocrine therapy in breast cancer patients whose expression of ER and PR has been converted from negative to positive by neoadjuvant chemotherapy.