Effect of the number of bone lesions on efficacy of zoledronic acid for prevention of skeletal-related events (SREs) in patients with bone metastases from solid tumors

Abstract

8529 Background: It has been postulated that greater numbers of bone metastases and thus greater tumor burden may lead to increased skeletal morbidity. To assess the effect that the number of baseline bone metastases may have on the efficacy of zoledronic acid in patients with solid tumors, we conducted a retrospective analysis of 3 large, randomized, controlled trials. Methods: Data were evaluated from the intent-to-treat population with breast cancer (n = 739), prostate cancer (n = 397), or lung cancer and other solid tumors (n = 480) who were treated with zoledronic acid 4 mg, pamidronate 90 mg, or placebo and had information available on number of baseline bone lesions. Patients were stratified into 2 groups: those with ≤ 3 bone lesions or > 3 lesions. Results: In general, patients with > 3 lesions had a higher skeletal morbidity rate (SMR) compared with patients with ≤ 3 lesions (Table 1), and zoledronic acid reduced SREs regardless of the number of bone lesions, but the benefit of zoledronic acid appeared greater in patients with > 3 lesions. In patients with lung cancer and other solid tumors who had > 3 bone lesions, zoledronic acid significantly reduced the mean SMR (P = .008) and significantly prolonged time to first SRE (median, 171 vs 84 day; P = .005) compared with placebo. In prostate cancer patients with > 3 bone lesions, zoledronic acid also significantly reduced the mean SMR compared with placebo (Table 1). In breast cancer patients with > 3 bone lesions, the mean SMRs were similar for zoledronic acid and pamidronate groups (Table 1). Conclusions: Patients with a greater number of bone lesions are at higher risk for skeletal complications and receive greater clinical benefit from treatment with zoledronic acid. [Table: see text] [Table: see text]