Women at risk for hip fracture following decline in bisphosphonate use.

Abstract

239 Background: Hip fractures in older adults are associated with increases in morbidity, mortality, and costs of care. Breast cancer treatment, including chemotherapy and endocrine treatment, interfere with bone health, increasing the risk of hip fracture for breast cancer survivors. Multiple studies report large and steady declines in hip fracture incidence coinciding with the availability of bisphosphonates to prevent osteoporosis, although black label warnings about side effects in 2011 steered physicians away from their widespread use. This study estimates trends in hip fracture incidence in a cohort of women with breast cancer before and after 2011. Methods: Retrospective observational study using 2007-2015 SEER-Medicare data for women aged 66 years or older continuously enrolled in fee-for-service Medicare with a first primary diagnosis of breast cancer. Primary outcome was an inpatient admission for a hip fracture within two years of cancer diagnosis. Monthly discrete time survival models were used to estimate the probability of hip fracture after diagnosis conditional on observable factors including demographic characteristics, comorbidities, and the concurrent use of bisphosphonates and cancer treatment. Results: A total of 67,577 patients met the inclusion criteria. The age adjusted incidence of hip fracture declined by 25.1% from 2007 to 2011; from 1093.662 (95% CI, 1027.9-1159.4) to 819.224 (95% CI, 762.1-876.4) per 100,000. However, the incidence of hip fractures stabilized after 2011, with a decline of only 4% from 2011 to 2014, when the incidence was 785.4 (95% CI, 728.6-842.1). The risk of hip fracture increases with age and the number of comorbid conditions. Although more women are prescribed bisphosphonates after a cancer diagnosis, prescription rates declined after 2011. Conclusions: The incidence of hip fractures in breast cancer survivors stabilized after years of steady declines. This significant change in incidence coincided with a large reduction in the use of bisphosphonates after warnings of rare but serious side effects were issued. More research is needed to prevent hip fracture in women with breast cancer and further consideration of available treatments is required for women at high risk for hip fracture.