Retrospective evaluation of the clinical benefit of long-term continuous use of zoledronic acid in patients with lung cancer and bone metastases

Abstract

Background: For patients with bone metastases, skeletal-related events including fracture are common, can cause considerable morbidity, and may reduce overall survival (OS). This retrospective analysis assessed the effect of Zometa (zoledronic acid, ZOL), an intravenous bisphosphonate (IV-BP), on fracture risk and OS in patients with bone metastases from lung cancer (LC). (Zometa is a registered trademark of Novartis Pharmaceuticals Corporation, USA.)

Methods: A claims-based analysis using commercial and Medicare Advantage data from >45 US managed-care plans was used to evaluate the association between fracture risk and treatment persistency (31-90, 91-180, 181-365, and ≥366 days) and follow-up duration in LC patients diagnosed with bone metastases between 01/01/2001 and 12/31/2006 and treated with ZOL or without (no IV-BP). Persistency was defined as the absence of a >45-day gap between ZOL treatments. Analysis of variance tests were used to compare follow-up duration, a proxy for OS, between ZOL persistency groups. The effect of time to treatment with ZOL was also assessed.

Results: In 9874 LC patients with bone metastases (n = 1090 ZOL; n = 8784 no IV-BP) the unadjusted relative fracture risk was reduced by 40% with ZOL vs no IV-BP; fracture risk decreased consistently with increasing duration of ZOL treatment. Even short-term (31-90 days) ZOL significantly reduced fracture risk (47%) vs no IV-BP (p = 0.005) with adjustment for differences in demographic and clinical characteristics. Delaying ZOL until after bone metastases were diagnosed significantly increased fracture risk (p = 0.0017). For a sub-set of patients included in a survival analysis (n = 550 ZOL; n = 4512 no IV-BP), mortality was significantly lower (mean, 38.6 vs 46.8 deaths/100 person-years; p = 0.038) in those treated with ZOL vs no IV-BP.

Limitations: Interpretation of this claims-based analysis must be tempered by the inherent limitations of observational data, such as limited clinical information and the ability to control for prognostic factors.

Conclusions: This retrospective analysis demonstrates that LC patients with bone metastases receiving ZOL had significantly reduced risk of fracture (p = 0.005) and death (p < 0.038) vs patients receiving no IV-BP. Longer ZOL persistency consistently yielded better outcomes, with ≥12 months' treatment producing the greatest benefit.