Positron emission tomography (PET) for staging of solitary plasmacytoma

Purpose: This study was undertaken to investigate the clinical value in staging patients with plasmacytoma (PC) using positron emission tomography (PET). Methods: Fifteen patients with known PC underwent PET using F-18 fluorodeoxyglucose (FDG-PET). FDG-PET was done for staging in 11 patients and for restaging in 4 patients. Eleven patients had PC of bone, and 4 patients had extramedullary PC. The results of all available imaging modalities, such as x-ray, magnetic resonance imaging (MRI), computed tomography (CT), bone scans, and of the clinical course, were used for verification of detected lesions. Results: Intensively increased tracer uptake was observed in 9 of 11 patients with bone lesions. One osteolytic lesion showed only slightly increased FDG-uptake and another PC of a rib (30 mm diameter) presented without FDG-uptake. The four extramedullary PC showed an intensively increased tracer uptake. In addition, 20 (10 confirmed) further plasmacytoma lesions, which were negative on the standard staging methods, were detected in 4 patients (27%). Since the diagnosis was changed from PC to multiple myeloma, a potentially curative local therapy was changed to a palliative systemic therapy. Conclusion: Although FDG-PET was false negative in I patient (7%) and indeterminate in another patient, additional lesions were detected in 5 (33%) of the patients, resulting in a change in the therapy regimen in 4 (27%) of the 15 patients.