The correlation between Fibrous Dysplasia/McCune-Albright syndrome (FD/MAS) skeletal disease burden on Na[18F]F-PET-CT and serum bone turnover markers (BTMs) was recently described. The effect of treatment on lesional fluoride burden in FD/MAS is unknown.To investigate treatment response measurements in FD/MAS patients who underwent Na[18F]F-PET-CT and treatment with antiresorptives.Observational case series.Academic center of expertise for rare bone diseases.15 consecutive patients with FD/MAS with baseline and follow-up Na[18F]F-PET-CT-parameters of healthy bone and FD lesions, BTMs and pain scores at start of denosumab (n=8) and non-denosumab patients (n=7).On Na[18F]F-PET-CT the Volumetric measures of FD-burden (FTV) and 'Fraction affected skeleton' (FAS), represented the portion of the skeleton affected. This was correlated with BTMs and pain.Disease activity decreased significantly, with FTV 361cm 3 to 97cm 3, p=0.018 in denosumab-treated patients, not in non-denosumab patients (p=0.249). Serum P1NP and Alkaline Phosphatase (ALP) decreased significantly: 82ng/mL vs 55ng/mL, p=0.023 and 119 IU/L vs 84 IU/L, p=0.020, respectively. In denosumab-treated patients pain scores improved leading to pain medication reduction. This correlated with lesional uptake whilst healthy bone activity did not change. BTMs and FTV correlated positively, P1NP r=0.730; p<0.001 and ALP r=0.406; p=0.006, as dis change in BTMs and FTV: P1NP (p=0.032) and ALP (p=0.024). FAS strongly correlated with treatment-induced decrease in ALP (p=0.027) and P1NP (p=0.009).Na[18F]F-PET-CT captured treatment-induced lesional changes which correlated with BTMs and pain reduction. Therefore Na[18F]F-PET-CT can be used as an objective local parameter of response to denosumab treatment in FD/MAS.
Wouter van der Bruggen, Dennis Vriens, Maartje E Meier, Frits Smit, Elizabeth M Winter, Lioe-Fee de Geus-Oei, Natasha M Appelman-Dijkstra