Risk of fracture in women treated with monthly oral ibandronate or weekly bisphosphonates: The eValuation of IBandronate Efficacy (VIBE) database fracture study

Abstract

The eValuation of IBandronate Efficacy (VIBE) head-to-head database fracture study compared fracture rates between patients treated with monthly ibandronate and weekly oral bisphosphonates (BPs).This large study included women ≥45 years old, newly prescribed monthly oral ibandronate or weekly oral alendronate or risedronate, and without malignancy or Paget's disease of bone. The primary analysis included patients who were adherent to treatment during the first 90 days after the index date. The risks of hip, nonvertebral, vertebral and any clinical fracture were compared using Cox proportional hazards models and adjusted for potential confounding factors. A secondary, “intent-to-treat” analysis included all patients who received at least one BP prescription. Sensitivity analyses based on the primary analysis compared patients receiving ibandronate with patients receiving weekly alendronate or risedronate separately, and explored the effect of excluding patients with potential confounding factors from the analysis. Further sensitivity analyses varied the requirement for adherence during the first 90 days after the index date.The primary analysis population included 7345 monthly ibandronate and 56,837 weekly BP patients. Fracture rates after the 12-month observational period were <2% and fracture risk was not significantly different between patients receiving monthly ibandronate or weekly BPs for hip, nonvertebral or any clinical fracture (adjusted relative risk: hip=1.06, p=0.84; nonvertebral=0.88, p=0.255; any clinical fracture=0.82, p=0.052). Ibandronate patients had a significantly lower risk of vertebral fracture than weekly BP patients (adjusted relative risk 0.36, 95% confidence interval 0.18–0.75, p=0.006). In the secondary, “intent-to-treat” analysis, relative risks of fracture were not significantly different between treatment groups for any fracture type. The results of the sensitivity analyses were generally consistent with the primary analysis.This retrospective cohort study found that patients treated with oral monthly ibandronate or weekly BPs (alendronate and risedronate) had similar, low risks of hip fracture, nonvertebral fracture and any clinical fracture. Ibandronate patients had a significantly lower relative risk of vertebral fracture than weekly BP patients; the clinical implications of these findings require further exploration and validation.