Bone Abstracts

Objectives: i) To evaluate the bone mineral density (BMD), and clinical outcomes of intravenous bisphosphonate treatment (IVT) and after treatment discontinuation in children with osteogenesis imperfecta (OI). ii) To compare the clinical outcome of those who discontinued IVT and those who had progressed from IVT to maintenance oral bisphosphonate therapy.

Methods: A retrospective study was conducted on 28 children with OI who had discontinued IVT (21 pamidronate and seven zoledronic acid). Data were collected at four time points: before treatment, before IVT discontinuation (IVD), 1 and 2 years after IVD. 21 patients (baseline mean age 5.2±3.7 years) were off therapy completely after IVD (group 1); seven patients (mean age 5.8±4.5) were switched to maintenance oral bisphosphonates (risedronate or alendronate) after IVD (group 2).

Results: Duration and number of IV infusions were similar in both groups (Group 1: 3.8±2.9 years, 11±8.0 infusions; Group 2: 3.93±2.4 years, 11±5 infusions). Lumbar BMD (LBMD) and total bone mineral content z-scores in all patients increased significantly from baseline to before IVD and were maintained for 2 years after IVD. There were no significant differences in LBMD z-scores, and the change in BMD parameters from before and 2 years after IVD between two groups. The fracture rates significantly reduced during the treatment, and increased slightly after IVD in both groups. In Group 1, height z-scores were preserved at 2 years after IVD. The rate of LBMD change from 1 to 2 years after IVD was positively correlated with duration of treatment (P=0.01) and number of infusions (P=0.03). Patients aged <5 years consistently had significantly higher LBMD z-scores over time compared to those >5 years (P=0.01).

Conclusions: IV bisphosphonate therapy significantly increased BMD and reduced fracture rate during the treatment. The beneficial effect in BMD was maintained for 2 years after discontinuation of IV therapy, with results as good as those switching to oral therapy. Younger age at the start of therapy, with longer duration and higher number of infusions was associated with greater BMD outcome after treatment discontinuation.

Disclosure: The authors declared no competing interests.