Survival in patients with multiple myeloma receiving zoledronic acid: Stratification by baseline bone alkaline phosphatase levels

7505 Background: Zoledronic acid is indicated for the treatment of bone metastases in patients with multiple myeloma and has been demonstrated to reduce the risk of skeletal morbidity. However, it is unknown whether there is a survival benefit secondary to the reduction in skeletal complications. To assess the effect of zoledronic acid on survival in patients with multiple myeloma, we conducted a retrospective analysis of a subset of patients in a large, randomized, controlled trial. Methods: Survival data were analyzed for multiple myeloma patients (n = 209) treated with zoledronic acid 4 mg (n = 107) or pamidronate 90 mg (n = 102) who had at least 1 post-baseline safety evaluation and information on baseline bone alkaline phosphatase (BALP) levels (a marker of bone metabolism). Patients were retrospectively stratified by baseline BALP levels according to the following criteria: low BALP (< 146 U/L) and high BALP (≥ 146 U/L). Survival data were analyzed over 25 months on study. Results: The overall survival rate at 25 months was significantly higher in patients treated with zoledronic acid compared with pamidronate (76% versus 63%; P = .038, Cox regression). Among patients who had a low baseline BALP level, the survival rates were similar for both treatment groups. However, among patients with a high baseline BALP level, zoledronic acid treatment significantly improved survival at study end compared with pamidronate (82% versus 55%; P = .048, log-rank test). Conclusions: This exploratory analysis suggests that zoledronic acid treatment may improve survival compared with pamidronate, and this effect was observed primarily in patients who had a high baseline BALP level, indicating more aggressive osteolytic disease. [Table: see text]