EFFECT OF TAMOXIFEN ON BONE-MINERAL DENSITY MEASURED BY DUAL-ENERGY X-RAY ABSORPTIOMETRY IN HEALTHY PREMENOPAUSAL AND POSTMENOPAUSAL WOMEN

Purpose: Tamoxifen is an effective treatment for metastatic and primar y breast cancer and is now being evaluated as a chemoprevention agent in healthy women. Any long-term effects on estrogen-sensitive tissues such as bone may have important therapeutic implications. Methods: We measured bone mineral density (BMD) in the lumbar spine and hip using dual-energy x-ray absorptiometry (DXA) in premenopausal and postmenopa usal healthy women who participated in our placebo-controlled tamoxife n chemoprevention of breast cancer trial. Results: BMD delta are now a vailable from 179 women for this analysis. In premenopausal women, BMD decreased progressively in the lumbar spine (P <.001) and in the hip (P <.05) for women on tamoxifen, but not those on placebo. The mean an nual loss in lumbar BMD per year over the 3-year study period in tamox ifen-treated compliant women who remained premenopausal throughout the study period was 1.44% (1.88% calculated on an intent-to-treat basis) compared with a small gain of 0.24% per annum for women on placebo (P < .001). Tamoxifen had the opposite effect in postmenopausal women. T he mean annual increase in BMD for women on tamoxifen was 1.17% in the spine (P <.005) and 1.71% in the hip (P <.001) compared with a nonins ignificant loss for women on placebo. Conclusion: These results indica te that tamoxifen treatment is associated with a significant loss of B MD in premenopausal women, whereas it prevents bone loss in postmenopa usal women. These adverse and beneficial effects of tamoxifen should b e considered in the assessment of the therapeutic benefits for both th e adjuvant treatment and the chemoprevention of breast cancer. (C) 199 6 by American Society of Clinical Oncology.