Use of intravenous bisphosphonates in older women with breast cancer

Introduction. i.v. bisphosphonates reduce skeletal events in women with bone metastases from breast cancer, but little is known about the prevalence and duration of bisphosphonate use. Methods. Patients were identified from the Surveillance, Epidemiology, and End Results-Medicare database who were aged ≥65 years and were diagnosed with invasive breast cancer in 1995-2002. Healthcare Common Procedure Coding System codes were used to identify patients treated with pamidronate and zoledronic acid. Descriptive statistics were used to describe patterns of use. Multivariate analyses were performed to determine the predictors of bisphosphonate use. Results. In total, 55,864 women with breast cancer were included, with 307,467 person-years of follow-up. Overall, 1.26% of women with all stages of breast cancer received i.v. bisphosphonates. In 2004, 2% of all breast cancer patients and 32% of patients with distant stage disease received bisphosphonates. Approximately two thirds of patients treated with bisphosphonates received zoledronic acid and one third received pamidronate in 2004. Multivariate analyses showed that patients who were ≥75 years old were less likely to receive bisphosphonates (75-79 years versus 65-69 years: odds ratio [OR], 0.81; 95% confidence interval [CI], 0.70-0.93; 80+ years versus 65-69 years: OR, 0.49; 95% CI, 0.42-0.57). The use of bisphosphonates dramatically increased over time. The majority of living patients were continued on i.v. bisphosphonates once started (83% at 1 year, 64% at 3 years, 50% at 5 years), but the median survival time after initiation of i.v. bisphosphonates was only 21 months. Conclusions. i.v. bisphosphonates appear to be under-used in patients with metastatic breast cancer, particularly among those patients >75 years of age.