Purpose: To explore the efficacy and safety of 500 mg of fulvestrant for the postmenopausal patients with estrogen receptor (ER)-positive metastatic breast cancer, and to analyze the factors affecting the prognosis of patients.
Methods: A retrospective analysis was conducted on the clinical data of 86 postmenopausal patients with ER-positive metastatic breast cancer, who were admitted to our hospital from January 2015 to December 2016, and these patients were treated with 500 mg of fulvestrant. The clinical efficacy and incidence of adverse reactions were evaluated. Moreover, the patients were followed up for recording the survival and disease progression. Finally, survival analysis was carried out using the Kaplan-Meier method, log-rank test and Cox's proportional hazards regression model.
Results: Among the 86 patients, 7 achieved partial response (PR), with an objective response rate (ORR) of 8.1%, and 44 (51.2%) had stable disease (SD), including 21 cases of SD ≥24 weeks, and the clinical benefit rate (CBR) [proportion of cases of complete response (CR) + PR +SD ≥24 weeks] was 36.0% (31/86). The remaining 35 (40.7%) patients suffered from progressive disease (PD) according to the initial efficacy assessment at 2-3 months after treatment. According to the follow-up results, the median overall survival (mOS) and median progression-free survival (mPFS) of patients were 26.7±6.9 months and 6.5±4.1 months, respectively. The 1-year and 2-year OS rates were 60.5% and 33.7%, respectively showing that the risk of PD in patients with visceral metastasis and taking tamoxifen was 2.443 times higher vs those not taking tamoxifen (p=0.031 vs (p=0.024). Besides, the mPFS was significantly prolonged in patients undergoing no endocrine therapy previously, and patients receiving first-line therapy of fulvestrant in this study [hazard ratio (HR) =1.942, 95% CI: 0.774-2.483, p=0.037, HR=0.863, 95% CI: 0.688-0.981, p=0.013).
Conclusion: Fulvestrant has definite efficacy in treating ER-positive metastatic breast cancer and results in tolerable adverse reactions, while it notably extends the mPFS of patients who have no visceral metastasis and receive no prior tamoxifen or endocrine therapy, but the first-line fulvestrant therapy in this study.