18F-FDG PET/CT in myeloma with presumed solitary plasmocytoma of bone

Aim: To evaluate the value of F-18-fluorodeoxyglucose (FDG) positron emission tomography with computed tomography (PET/CT) in myeloma in patients presenting with a solitary plasmacytoma of bone (SPB). Patients and Methods: Fourteen consecutive patients studied since 2006, all having a diagnosis of SPB before PET/CT imaging took part in this study. In 3 patients PET/CT was performed for staging while in the remaining 11 it was used to monitor therapy. PET/CT was performed using a dedicated tomograph 60-90 minutes after intravenous injection of 5.3 MBq/kg of F-18-FDG and the results were compared to other diagnostic procedures [radiographs and magnetic resonance imaging (MRI)], biopsy, and other available follow-up data. Results: In 8/14 patients, PET/CT scans showed previously unsuspected sites of increased FDG accumulation. In 618 patients, FDG uptake was considered pathologic, depicting myeloma involvement in bone, while in the remaining cases, findings were considered incidental and not related to myeloma. PET findings attributed to myeloma were confirmed (i.e. true positives) in 6/6 cases (100%) and in all patients with findings reported as non-pathologic, myeloma was excluded (100% true negatives). Conclusion: Our preliminary data in a small number of cases suggests that there are a group of patients with SPB (local disease) in whom FDG PET/CT may detect other unsuspected sites of bone involvement, upstaging the extent of the disease. In these cases, SPB may be a local manifestation of multiple myeloma where other sites of involvement have eluded detection by other less sensitive imaging modalities (i.e. skeletal surveys) or anatomically restricted imaging (i.e., less than total body MR or CT). Finding other sites of involvement have significant implications for appropriate treatment of myeloma.