Response to Zoledronic Acid in Patients with Active Paget's Disease of Bone: A Retrospective Study

BACKGROUND: Traditionally, bisphosphonates are used to treat active Paget's disease of bone (PDB). Intravenous zoledronic acid (ZA) is the most effective treatment option leading to sustained remission. OBJECTIVE: The primary objective of this study was to analyze the effect of intravenous ZA in patients with active PDB in a tertiary care center of India. MATERIALS AND METHODS: Retrospective data of 13 patients with active PDB who received a single dose of 4 mg intravenous ZA at our institute from January 2011 to June 2017 were reviewed. Response to therapy was monitored clinically, biochemically by serum alkaline phosphatase (ALP), and scintigraphically by 99m-Technetium methylene diphosphonate bone scan. RESULTS: All of our patients reported relief of bone pain. The mean duration of follow-up in our study was 35.2 ± 16.8 months. Serum ALP levels reduced significantly from 1190.9 ± 666.1 IU/L (n = 13) at baseline to 200.5 ± 68.4 IU/L (n = 13) at 6 months (P < 0.001). ALP level at 1 year was 174 ± 33.6 IU/L (n = 12), which remained stable till 36 months at 176.5 ± 50 IU/L (n = 8). This indicates that remission achieved by 6 months post ZA is sustained for at least 3 years. Scintigraphic ratio reduced from 9.6 [interquartile range (IQR) 5.25–18.2] at baseline to 2.7 (IQR 1.20–4.05) at follow-up (P < 0.001). Similarly, scintigraphic index of involvement reduced from 9.9 (IQR 5.6–28.5) at baseline to 3 (IQR 2–4) at follow-up (P = 0.018). CONCLUSION: A 4 mg single dose of intravenous ZA results in clinical, biochemical, and scintigraphic response that is sustained for at least 3 years.