P3-15-02: The Change of Bone Turnover Markers during Neoadjuvant Anastrozole Versus Exemestane: A Randomized Single-Center Study.

Abstract

Abstract Background: Non-steroidal aromatase inhibitors including anastrozole and letrozole have been reported to increase the rate of bone turnover, accelerate loss of bone, and increase the incidence of fractures. Although steroidal inactivator exemestane has similar inhibitory effect on the aromatization, animal studies have shown a weak but potentially important anabolic effect of exemestane metabolites, which might lead to decreased bone resorption. This randomized trial was conducted to compare the effect of exemestane and anastorozole on bone turnover markers. Patients and Methods: Fifty-two postmenopausal women with ER-positive, HER2−negative, invasive, nonmetastatic, and operable breast cancer were randomly assigned to neoadjuvant exemestane (25 mg daily) or anastrozole (1 mg daily) for 4 months. The primary endpoint was change in bone turnover markers including resorption markers urinary and serum N-telopeptide (NTX) and the formation markers serum bone alkaline phosphatase (BAP). The secondary endpoint was tumor objective response (OR) assessed by both caliper and ultrasound. Comparisons were also made of breast conservation rate and adverse events. Results: The changes in serum NTX from baseline to week 16 were not statistically different between anastrozole and exemestane. The changes in urinary NTX from baseline to week 16 were also not statistically different between both groups .BAP did not show any significant increase in the exemestane group (10.8%; p=0.21), whereas the increase in BAP from baseline to week 16 in the anastrozole group was 15.0% and marginally significant (p=0.05). There were no significant differences in OR in the intent-to-treat population between patients receiving anastrozole or exemestane (45.8% vs. 39.2%; p=0.63). The OR was similar between the patients with a baseline Ki67 index of ≥15% and <15% in exemestane group (37.5% vs. 41.2%; p=0.86). In anastrozole group the OR in patients with a baseline Ki67 index of ≥15% and <15% was 44.4% and 53.8%, respectively(p=0.66). Breast conservation rate was similar between anastrozole and exemestane (62.5% vs. 67.9%; p=0.68). Treatment was well tolerated and much the same for both groups. Conclusions: There is no significant differences of the change in bone turnover markers between anastrozole and exemestane. These results indicate exemestane had no anabolic effects which would lead to fewer adverse effects on bone. Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P3-15-02.