Effects of Exemestane, Anastrozole and Tamoxifen on Bone Mineral Density and Bone Turnover Markers in Postmenopausal Early Breast Cancer Patients: Results of N-SAS BC 04, the TEAM Japan Substudy

<i>Background:</i> Use of aromatase inhibitors in women with postmenopausal breast cancer accompanies risks of bone loss. We evaluated changes in bone mineral density (BMD) and bone turnover markers in patients treated with exemestane, anastrozole or tamoxifen for hormone-sensitive postmenopausal early breast cancer. <i>Patients and Methods:</i> Sixty-eight patients enrolled in the Tamoxifen Exemestane Adjuvant Multinational Japan bone substudy were randomly assigned to receive tamoxifen, exemestane or anastrozole. During a 2-year study period, lumbar spine BMD was measured using dual-energy X-ray absorptiometry, and urinary type I collagen cross-linked N-telopeptide (NTX) and serum bone-specific alkaline phosphatase (BAP) were also measured. <i>Results:</i> BMD at 2 years of treatment was higher in tamoxifen patients compared with exemestane and anastrozole patients; however, the intergroup difference was not significant (p = 0.2521 and p = 0.0753, respectively). BMD was higher in exemestane patients compared with anastrozole patients; however, the intergroup difference was not significant (p = 0.7059 and p = 0.8134, respectively). NTX and BAP were significantly lower in tamoxifen patients compared with exemestane and anastrozole patients at 1 and 2 years of treatment (p < 0.05). <i>Conclusion:</i> Tamoxifen may provide better bone protection compared with exemestane or anastrozole. The effect of exemestane and anastrozole on bone loss may be comparable in Japanese postmenopausal women.