Aromatase Inhibitor-associated Bone Loss in Breast Cancer Patients is Distinct from Postmenopausal Osteoporosis

Women with breast cancer are increasingly being diagnosed and treated earlier in the disease process, resulting in significantly improved clinical outcomes. Aromatase inhibitor (AI) therapy has shown superior efficacy compared with tamoxifen in postmenopausal women and is quickly becoming the therapy of choice in this setting. However, adjuvant AI therapy depletes residual estrogen and is associated with rapid bone loss and increased fracture risk distinctly different from those observed in postmenopausal osteoporosis. Aromatase inhibitor-associated bone loss (AIBL) occurs at a rate at least 2-fold higher than bone loss seen in healthy, age-matched postmenopausal women, resulting in a significantly higher fracture incidence regardless of the AI administered. Thus, antiresorptive treatments designed to address postmenopausal osteoporosis may not be sufficient in this unique population. Furthermore, current guidelines for the management of bone health in women with breast cancer may not correctly identify patients who may benefit from therapy. Consequently, breast cancer patients receiving adjuvant AI therapy will require specialized management strategies to identify and treat patients at high risk for fracture. Recently, nitrogen-containing bisphosphonates have emerged as the treatment of choice for the prevention of AIBL and the reduction of fracture risk in this setting.