Abstract P1-16-01: Skeletal-related events (SRE) prevented in breast cancer patients with bone metastases in the United States (US)

Abstract

Abstract Background: SREs are potentially debilitating consequences of bone metastases in advanced stage cancers. Bone-targeting agents (BTAs), including denosumab and intravenous zoledronic acid (ZA) are approved to prevent SREs. The purpose of this study was to estimate the annual number of SREs that might occur in US women with breast cancer without intervention, and to estimate the SREs that could be prevented with denosumab or with ZA. Methods: A model was developed using US prevalence estimates (Li, et al. 2011), combined with 2012 Census projections to estimate the number of SREs in women with bone metastases from breast cancer in 2012. SREs were defined as fracture, radiation to bone, surgery to bone, or spinal cord compression. The SRE rate in untreated patients was estimated by pooling rates from 8 treatment groups in 4 trials (Lipton 2000; Rosen 2003; Kohno 2005; Stopeck 2010), applying the appropriate relative hazard (RH) of first and subsequent SRE from a network meta-analysis (NMA;Ford 2012), and weighting by the sample size. The denosumab and ZA SRE rates were derived from the pooled rate and the RH estimates from the NMA. Ineligibility was defined as one of the following: all uninsured patients (US Census) and patients discontinuing due to adverse events or non-compliance (ZA 4.6%, denosumab 3.7%; Stopeck 2010). Patients with kidney clearance < 30 ml/min (1.3%; Launay-Vacher 2007) were considered ineligible to receive ZA. Using Monte Carlo sampling, we derived mean estimates and 95% simulation intervals (SI) based on 1,000 samples. Results: Overall, we estimated 96,598 women with breast cancer had bone metastases at any given time in 2012. We estimated 164,673 (95% SI 110,153 to 220,770) SREs would have occurred in 2012 if no women were treated. Assuming all women eligible to receive ZA were treated with ZA (n = 83,870), the number of SREs would have been 108,233 (decline of 56,440, 95% SI 13,744 to 100,098); assuming all women eligible to received denosumab were treated with denosumab (n = 85,780), the number of SREs would have been 86,992 (decline of 77,681, 95% SI 38,327 to 120,521). The incremental difference between denosumab and ZA was 21,242 (95% SI 9,312 to 36,674). Conclusions: The use of BTAs to reduce SRE risk, including denosumab, could result in reductions in the number of adverse skeletal complications in the US. Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P1-16-01.