Assessing the risk of bone fracture among postmenopausal women who are receiving adjuvant hormonal therapy for breast cancer

Objective: To understand better the true impact of widespread adoption of adjuvant aromatase inhibitor (Al) therapy on postmenopausal breast cancer patients' risk of bone fracture. Methods: Data from three different studies were used to estimate the relative risk of bone fracture for each of the following groups of women (i.e., versus a control group of healthy postmenopausal women): (a) healthy postmenopausal women receiving tamoxifen; (b) postmenopausal women who had received treatment for early breast cancer; (c) postmenopausal breast cancer patients on adjuvant tamoxifen therapy; (d) postmenopausal breast cancer patients on adjuvant anastrozole therapy. The results of these analyses were then used to estimate the likely incidence of clinical fracture among such populations in 'real-life' clinical practice. Results: Breast cancer survivors were calculated to be at increased risk of clinical bone fracture (i.e., RR 1.15 vs. control group over 5 years). Breast cancer patients initiated on adjuvant anastrozole were also calculated to be at increased risk of bone fracture (RR = 1.36 vs. control group over 5 years), while the calculated risk of fracture among tamoxifen-treated breast cancer patients was similar to that observed in the control population (RR = 0.91). Conclusion: Breast cancer patients are at increased risk of clinical bone fracture (compared with the general postmenopausal population) and adjuvant anastrozole therapy slightly adds to this risk. Importantly, however, the absolute risk of bone fracture appears to remain low in each of the evaluated patient populations, suggesting that fear of fracture should not prevent the initiation of adjuvant aromatase inhibitor therapy.