Fluorine-18-FDG PET in Paget's disease of bone

Paget's disease of bone is common in the elderly and is associated with increased osteoblastic and osteoclastic activity at affected sites in the skeleton. It is not known whether this high metabolic activity is associated with increased glycolysis and, hence, uptake of [18F]FDG. The appearances of Paget's disease with [18F]FDG PET have not been described and it is not known whether Paget's may cause false-positive studies in those undergoing oncological staging or whether [18F]FDG PET can reliably differentiate benign pagetic change from osteosarcoma that may complicate Paget's disease. We reviewed [18F]FDG PET scans in patients with uncomplicated Paget's disease and documented its appearances.

Eighteen patients with established Paget's disease and typical radiological features had 99mTc-MDP bone scans and [18F]FDG PET scans performed. Serum alkaline phosphatase (ALP) was also measured.

All patients showed high uptake of MDP in affected bones. Of the 18 patients only six showed any uptake of [18F]FDG. This occurred in some but not all bones shown to be involved on MDP bone scans. Three patients demonstrated low-grade uptake and three showed marked accumulation of [18F]FDG. The [18F]FDG-positive group had higher serum ALP levels than the [18F]FDG-negative patients (p < 0.05).

Paget's disease of bone is not associated with abnormal [18F]FDG uptake in the majority of patients and, therefore, there is potential for discriminating between benign Paget's disease and associated Paget's sarcoma. However, low-grade uptake may be seen in patients with more active disease as measured by ALP. Rarely, marked uptake of [18F]FDG may be seen and Paget's disease should be included as a possible cause of false-positive scans in elderly patients who are being assessed for metastatic disease.