Long-term effects of aromatase inhibitors on bone.

The risk of fracture in the postmenopausal woman given aromatase inhibitors may be increased by up to 60%. This is likely to be true for all third generation drugs, but the clinical trials did not include sufficient fracture events for certainty on this issue. It would appear that most of the excess fracture risk relates to vertebral fracture and in future studies, more effort should be given to ascertaining these fractures. The likely mechanism for the increase in fracture risk is an increase in bone turnover (of about 20%) and an acceleration of bone loss. There is evidence to suggest that the residual levels of oestradiol present in the postmenopausal woman are important for bone health, and thus, the effect of these drugs is to remove this protective effect. Current clinical practice should include the measurement of bone mineral density in postmenopausal women taking these drugs and commencement of antiresorptive therapy if osteoporosis is already present.