Efficacy and Safety of Bisphosphonate Therapy in Mccune-Albright Syndrome–Related Polyostotic Fibrous Dysplasia: A Single-Center Experience

Abstract

Fibrous dysplasia (FD) is a rare disorder characterized by pain, deformity, and pathologic fractures. McCune-Albright syndrome (MAS) includes a combination of FD, hyperfunctional endocrinopathy, and/or café-au-lait pigmentation. Surgery is generally ineffective in treating FD. This study aimed to evaluate the efficacy and safety of bisphosphonates (BPs) and compare the efficacy of different BPs in FD patients. In this retrospective clinical study, laboratory and clinical findings of 22 polyostotic FD cases all associated with MAS were recorded before and after therapy with BPs. Within the first year of therapy with BPs, the level of alkaline phosphatase (ALP) decreased by 30.3% of baseline in the alendronate cases and by 22.7 ± 16.9% and 34.1 ± 26.3% in the pamidronate (PAM) (n = 10) and zoledronic acid (ZA) (n = 11) groups, respectively. There was no significant difference ( P = .256) between the PAM and ZA groups in the rate of change in ALP levels. Bone pain was alleviated in 64% of the cases. Number of affected bones was positively correlated with baseline serum ALP levels ( r = 0.533; P = .011), which was the only significant factor affecting efficacy of BPs. BP treatment was safe and caused no obvious impairment on children's linear growth. Our results suggest that BPs may suppress high bone turnover to partially control the activity of the disease and are well tolerated in most patients. ZA has similar effects as PAM in controlling disease activity. ALP = alkaline phosphatase; β-CTX = C-terminal telopeptide of type I collagen; BP = bisphosphonate; BTM = bone turnover marker; FD = fibrous dysplasia; MAS = McCune-Albright syndrome; ONJ = osteonecrosis of the jaw; PAM = pamidronate; PFD = polyostotic fibrous dysplasia; ULN = upper limit of normal; ZA = zoledronic acid.