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Increased Fracture Risk in Women Treated With Aromatase Inhibitors Versus Tamoxifen: Beneficial Effect of Bisphosphonates.

  • Pineda-Moncusí, Marta1
  • Garcia-Giralt, Natalia1
  • Diez-Perez, Adolfo1, 2
  • Servitja, Sonia3, 4
  • Tusquets, Ignasi3, 4
  • Prieto-Alhambra, Daniel5, 6
  • Nogués, Xavier1, 2
  • 1 Hospital del Mar Research Institute (IMIM), Centro de Investigación Biomédica en Red de Fragilidad y Envejecimiento Saludable (CIBERFES), Barcelona, Spain. , (Spain)
  • 2 Internal Medicine Department, Hospital del Mar, Universitat Autònoma de Barcelona, Barcelona, Spain. , (Spain)
  • 3 Cancer Research Program, Hospital del Mar Research Institute (IMIM), Barcelona, Spain. , (Spain)
  • 4 Medical Oncology Department, Hospital del Mar, Barcelona, Spain. , (Spain)
  • 5 Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, Centre for Statistics in Medicine, University of Oxford, Oxford, UK.
  • 6 Grup de Recerca en Malalties Prevalents de L'Aparell Locomotor (GREMPAL) Research Group and CIBERFES, University Institute for Primary Care Research (IDIAP) Jordi Gol, Universitat Autònoma de Barcelona and Instituto de Salud Carlos III, Barcelona, Spain. , (Spain)
Published Article
Journal of Bone and Mineral Research
Wiley (John Wiley & Sons)
Publication Date
Oct 09, 2019
DOI: 10.1002/jbmr.3886
PMID: 31596961


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 (subdistribution hazard ratio [SHR] [95% CI]). In postmenopausal women, fracture risk in aromatase inhibitor users showed an HR 1.40 [95% CI,1.05 to 1.87] and SHR 1.48 [95% CI, 1.11 to 1.98], compared to tamoxifen. Observing aromatase inhibitors patients at high risk of fracture, bisphosphonate-treated patients had an HR 0.73 [95% CI, 0.51 to 1.04] and SHR 0.69 [95% CI, 0.48 to 0.98] compared to nontreated. 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 nonbisphosphonate users. Monitoring fracture risk and related risk factors in aromatase inhibitor patients is advisable. © 2019 American Society for Bone and Mineral Research. © 2019 American Society for Bone and Mineral Research.

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