Clinical Epidemiology (Sep 2018)

Use of bone-modifying agents among breast cancer patients with bone metastasis: evidence from oncology practices in the US

  • McGrath LJ,
  • Overman RA,
  • Reams D,
  • Cetin K,
  • Liede A,
  • Narod SA,
  • Brookhart MA,
  • Hernandez RK

Journal volume & issue
Vol. Volume 10
pp. 1349 – 1358

Abstract

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Leah J McGrath,1 Robert A Overman,1 Diane Reams,1 Karynsa Cetin,2 Alexander Liede,3 Steven A Narod,4 M Alan Brookhart,1 Rohini K Hernandez2 1NoviSci, LLC, Durham, NC, USA; 2Amgen Inc, Thousand Oaks, CA, USA; 3Amgen Inc, South San Franscisco, CA, USA; 4Department of Medicine, University of Toronto, Toronto, Canada Purpose: Bone-modifying agents (BMAs) are recommended for women with bone metastasis from breast cancer to prevent skeletal-related events. We examined the usage patterns and identified the factors associated with the use of BMAs (denosumab and intravenous bisphosphonates) among women in the US. Patients and methods: Electronic health records from oncology clinics were used to identify women diagnosed with bone metastasis from breast cancer between 2013 and 2014. Patients were excluded if they had recently used a BMA or had concurrent cancer at an additional primary site. The incidence of BMA initiation, interruption, and reinitiation were estimated using competing risk regression models. A generalized linear model was used to estimate risk factors for treatment initiation and interruption. Results: There were 589 women diagnosed with bone metastasis from breast cancer. By 1 year, 68% of these patients (95% CI: 64%, 71%) had initiated treatment with a BMA. Denosumab and zoledronic acid were the most commonly used agents, whereas pamidronate was used infrequently. Young women were more likely to initiate a BMA than older women (adjusted risk difference: 6.4 [95% CI: 1.5, 10.9]). Of the 412 patients who initiated a BMA, 46% (95% CI: 41%, 51%) experienced an interruption within 1 year. Seventy-four percent (95% CI: 68%, 79%) of patients who interrupted their treatment had reinitiated therapy within 1 year of interruption. Conclusion: The majority of women diagnosed with bone metastasis from breast cancer initiate a BMA within 1 year of diagnosis, but a large proportion, particularly among the elderly, do not use these therapies. Keywords: bone-modifying agents, breast cancer, bone metastasis, treatment patterns, electronic health records, denosumab, zoledronic acid, pamidronate

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