Increased Fracture Risk in Women Treated with Aromatase Inhibitors versus Tamoxifen: Beneficial Effect of Bisphosphonates.
J Bone Miner Res. 2019 Oct 09;: Authors: Pineda-Moncusí M, Garcia-Giralt N, Diez-Perez A, Servitja S, Tusquets I, Prieto-Alhambra D, Nogués X
Aromatase inhibitors have been associated with accelerated bone loss and an increased risk of osteoporotic fractures. Currently, bisphosphonates are recommended to reduce fracture risk in these patients. The aim of this study is to evaluate the fracture risk in breast cancer patients receiving aromatase inhibitors, compared to tamoxifen users, and to assess the effectiveness of oral bisphosphonates in reducing fracture risk. We performed an observational cohort study up to 10 years of follow-up. Data were extracted from primary care records in a population database. Women diagnosed with breast cancer between 2006 and 2015 and treated with tamoxifen or aromatase inhibitors (n = 36,472) were stratified according to low (without osteoporosis diagnosis nor bisphosphonates exposure) or high (with osteoporosis and/or treated with bisphosphonates) fracture risk. Cox models were used to calculate hazard ratios (HR [95%CI]) of fracture from the propensity score matched patients. Sensitivity analyses account for competing risk of death were performed (SHR [95%CI]). In postmenopausal women, fracture risk in aromatase inhibitor users showed a HR: 1.40 [1.05 to 1.87] and SHR: 1.48 [1.11 to 1.98], compared to tamoxifen. Observing aromatase inhibitors patients at high-risk of fracture, bisphosphonate treated patients had a HR: 0.73 [0.51 to 1.04] and SHR: 0.69 [0.48 to 0.98] compared to non-treated. In conclusion, fracture risk in postmenopausal women during aromatase inhibitor treatment, in real-life conditions, was >40% compared to tamoxifen, corroborating previous randomized controlled trials results. In high-risk patients, bisphosphonate users had lower significant fracture incidence during aromatase inhibitor therapy than non-bisphosphonate-users. Monitoring fracture risk and related risk factors in aromatase inhibitor patients is advisable. This article is protected by copyright. All rights reserved. PMID: 31596961 [PubMed - as supplied by publisher]