Exemestane Use in Postmenopausal Women at High Risk for Invasive Breast Cancer: Evaluating Biomarkers of Efficacy and Safety

Abstract

This phase II trial evaluated clinical markers of efficacy and safety of exemestane in postmenopausal women at increased risk for breast cancer. Postmenopausal women (n = 42) at risk for invasive breast cancer received 25 mg exemestane daily for 2 years along with calcium and vitamin D. The primary outcome was change in mammographic density (MD) after one year. Secondary outcomes included change in serum steroid hormones as well as change in trefoil protein 1 (TFF1) and proliferating cell nuclear antigen (PCNA) in breast tissue. Safety and tolerability were also assessed. MD decreased at 1 year and was significant at 2 years [mean change = -4.1%; 95% confidence intervals (CI), -7.2 to -1.1; P = 0.009]. Serum estradiol and testosterone levels significantly decreased at 3 months and remained suppressed at 12 months. After 1 year of treatment, TFF1 intensity decreased (mean change -1.32; 95% CI, -1.87 to -0.76; P < 0.001). Exemestane was safe and well tolerated. Exemestane decreased MD and expression of breast tissue TFF1. It was well tolerated with few clinically relevant side effects. MD and breast tissue TFF1 are potential biomarkers of breast cancer-preventive effects of exemestane in high-risk postmenopausal women.

Trial registration: ClinicalTrials.gov NCT00073073.

Figure 1

Study Enrollment

Figure 2a

Down-regulation of TFF1 in normal breast tissue after 12 months of treatment with exemestane.

Figure 2b

Down-regulation of TFF1 intensity in normal breast tissue after 12 months of exemestane. (n=22;1 bar = 1 subject) TFF1 is down-regulated after 12 months of treatment with Exemestane. Pre-treatment images were scored +3 (intense) TFF1 staining and post-treatment images as +1 (weak) TFF1 staining. All images magnified at 40x.