¹⁸F-NaF PET/CT IMAGING IN FIBROUS DYSPLASIA OF BONE

Fibrous dysplasia (FD) is a mosaic skeletal disorder resulting in fractures, deformity, and functional impairment. Clinical evaluation has been limited by a lack of surrogate endpoints capable of quantitating disease activity. The purpose of this study was to investigate the utility of ¹⁸F-NaF PET/CT imaging in quantifying disease activity in patients with FD. Fifteen consecutively evaluated subjects underwent whole-body ¹⁸F-NaF PET/CT scans, and FD burden was assessed by quantifying FD-related ¹⁸F-NaF activity. ¹⁸F-NaF PET/CT parameters obtained included (i) SUV_max (standardized uptake value [SUV] of the FD lesion with the highest uptake); (ii) SUV_mean (average SUV of all ¹⁸F-NaF–positive FD lesions); (iii) total volume of all ¹⁸F-NaF–positive FD lesions (TV); and (iv) total FD lesion activity determined as the product of TV multiplied by SUV_mean (TA = TV × SUV_mean) (TA). Skeletal outcomes, functional outcomes, and bone turnover markers were correlated with ¹⁸F-NaF PET/CT parameters. TV and TA of extracranial FD lesions correlated strongly with skeletal outcomes including fractures and surgeries (p values ≤ 0.003). Subjects with impaired ambulation and scoliosis had significantly higher TV and TA values (P < 0.05), obtained from extracranial and spinal lesions, respectively. Craniofacial surgeries correlated with TV and TA of skull FD lesions (P < 0.001). Bone turnover markers, including alkaline phosphatase, N-telopeptides, and osteocalcin, were strongly correlated with TV and TA (P < 0.05) extracted from FD lesions in the entire skeleton. No associations were identified with SUV_max or SUV_mean. Bone pain and age did not correlate with ¹⁸F-NaF PET/CT parameters. FD burden evaluated by ¹⁸F-NaF-PET/CT facilitates accurate assessment of FD activity, and correlates quantitatively with clinically-relevant skeletal outcomes.