Impact of zoledronic acid (ZA) versus pamidronate (P) on overall survival (OS) in multiple myeloma (MM).

Abstract

e17546 Background: Nitrogen-containing bisphosphonates (BPs) have been shown to improve OS compared to non-nitrogen containing BPs in MM (Morgan et al. Lancet 2010). Treatment guidelines recommend use of ZA or P (both nitrogen-containing) in MM patients with bone disease. No study has compared the effect of these two drugs on OS. We compared the impact of ZA versus P on OS in United States Veterans with MM. Methods: We retrospectively identified patients diagnosed with MM from 10/2002-2/2009 within the Veterans Heath Administration Central Cancer Registry who received ZA (n=482) or P (n=757) by linking registry data to pharmacy records. Cox multivariable analysis was used to estimate the association between choice of BP and OS while controlling for potential confounders: body mass index (BMI), age, race, Charlson comorbidity index, year, treatment, hemoglobin (Hgb), creatinine (Cr), and albumin. Results: The median OS in patients receiving ZA was 34.5 months, compared to 26.4 months in the P group. After adjusting for confounders, ZA reduced the risk of death by 24% compared to P (hazard ratio [HR] 0.76; 95% confidence interval [CI]: 0.66-0.88) at 5 years (Table). A sensitivity analysis that compared ZA only (n=482) versus all patients who received P, regardless if they later received ZA (n=1117) continued to show decreased mortality (HR 0.82; 95% CI: 0.71-0.94) after controlling for the same potential confounders. Conclusions: In this, the largest study to evaluate the association between ZA versus P on OS in MM, we found decreased mortality associated with ZA. Given the similar toxicity profiles, this study supports preferential use of ZA over P and may serve as evidence for re-evaluation of current guidelines for BP use in MM. [Table: see text]