Effects of tamoxifen on spinal bone density in women with breast cancer.

Bone densitometry (L2-L4) was performed on 10 postmenopausal women with breast cancer after 0, 6, and 12 months of tamoxifen treatment; the results were compared with data from 10 normal controls. The patients and controls differed significantly at 6 (P less than .05) and 12 (P less than .003) months. The tamoxifen group showed a nonsignificant mean gain in bone mineral density after 6 and 12 months of treatment (+0.024 +/- 0.014 and +0.022 +/- 0.018 g/cm2, respectively), whereas the controls showed a nonsignificant mean loss of bone mass at 6 months (-0.012 +/- 0.018 g/cm2) and a statistically significant loss of bone density after 12 months (-0.024 +/- 0.01 g/cm2). These preliminary data suggest that tamoxifen use is associated with preservation of bone mass during the first year of treatment.