Effect of estrogen agonist antagonist on bone mineral density in postmenopausal breast cancer

ABSTRACT

Tamoxifen is an estrogen agonist/ antagonist, which has its effect not only on breast cancer cells but also on the liver and bone. In this study we tried to study the effect of long-term treatment with that drug on bone metabolism. Twenty-five postmenopausal women with stage I or II breast cancer receiving 30 mg tamoxifen daily together with twenty-five postmenopausal age-matched normal controls were included in this study. Measurements of bone mineral density using dual energy X-ray absorptiometry [DEXA] at the lumbar spine, femoral neck and forearms were done after the operation, at the start of the study and after 12 months of tamoxifen administration. They were compared with those of normal controls. Bone mineral density increased in the tamoxifen treated group as compared to the control group. A decrement in bone mineral density in the age-matched group [Z score] was statistically significant [p<0.05]. Also, there was a significant reduction in serum cholesterol in the tamoxifen treated group. These results indicate that tamoxifen has estrogen-like effects on bone metabolism in post-menopausal women. This results in an increase and stabilization of bone mineral density in the axial skeleton and a stabilization of bone mineral content in the appendicular skeleton