Assessment of zoledronic acid treatment patterns and clinical outcomes in patients with bone metastases from genitourinary cancers

Abstract

Background:

Patients with bone metastases secondary to genitourinary (GU) cancer are at risk for skeletal-related events (SREs), including bone pain requiring palliative radiotherapy, fractures or surgery to bone, spinal cord compression, and hypercalcemia of malignancy. These SREs can be debilitating and potentially life-limiting. This study examined treatment practices and the association of treatment patterns with Zometa (zoledronic acid, ZOL), an intravenous bisphosphonate (IV-BP), with SREs and fractures. (Zometa is a registered trademark of Novartis Pharmaceuticals Corporation, USA.)

Methods:

Retrospective analysis of commercial and Medicare Advantage enrollment and medical claims data was performed to evaluate IV-BP use and SRE patterns in adult patients with GU cancers. Criteria included diagnosis of ≥1 bone metastasis and prostate cancer (PC), renal cell carcinoma (RCC), or bladder cancer (BlC) between January 2001 and December 2006; continuous healthcare plan enrollment for ≥6 months before the index date; and no evidence of prior IV-BP use. Patients were followed until disenrollment from the healthcare plan or December 2007.

Results:

Of 6347 patients (PC, n?=?4976; RCC, n?=?941; BlC, n?=?430; mean standard deviation] age: 68.9 11.1] years), only ～23% received ZOL. The mean time between diagnosis of bone metastasis and ZOL initiation was ～108 days. Among patients with PC, fracture risk was significantly smaller for ZOL vs no IV-BP (incidence rate ratio?=?0.70; p?<?0.001), and 2-year survival was significantly longer for ZOL-treated vs no IV-BP patients (p?=?0.007). Patients with longer persistency on ZOL had a smaller fracture risk than patients with shorter persistency. Sub-set analyses were not performed for RCC and BIC because the proportion of patients treated was too low.

Limitations:

Interpretation of this claims-based analysis must be tempered by the inherent limitations of observational data, such as limited and accurate available information, and unavailable information including clinical or disease-specific parameters.

Conclusions:

Intravenous BP therapy is not always received in patients with bone metastases secondary to GU cancers, and, when used, there are typically long time periods before treatment initiation. Without IV-BPs, PC patients have significantly larger risks of fracture and death compared with ZOL-treated patients, and benefits appear to be larger with increasing persistency on ZOL.