Long term effects on biochemical bone markers of a single infusion of zoledronic acid in Paget disease of bone

The aim of the present study is to evaluate long term biochemical response to a single dose of zoledronic acid in patients with Paget disease of bone, as well as evaluating the value of bone turnover markers in diagnosis and follow-up. This is an observational, descriptive and prospective study. Included patients received a single-dose intravenous infusion of 5 mg zoledronic acid. Bone turnover markers were measured at baseline, and in every follow up visit. Thirty-nine patients with a mean follow-up of 56.49 months were included. At the time Paget disease was diagnosed, all of the patients (100%) had high serum procollagen type 1 amino-terminal propeptide values, but not all patients had high serum C-terminal telopeptide and alkaline phosphatase values (85% and 89% respectively). Biochemical response to therapy occurred in 38 out of 39 patients (97%). Two patients had partial response at 6 months but complete response thereafter. Only one patient relapsed (nadir procollagen type 1 amino-terminal propeptide 35.06 μg/l, value at relapse 75.2 μg/l) 4.5 years after treatment. Values of serum C-terminal telopeptide and alkaline phosphatase of this patient were normal despite P1NP relapse. We hence conclude that zoledronic acid is effective in inducing and maintaining biochemical remission and that procollagen type 1 amino-terminal propeptide is a better diagnostic and prognostic marker in PDB when compared to C-terminal telopeptide and alkaline phosphatase.