Positron emission tomography (PET) for staging of solitary plasmacytoma

This study was undertaken to investigate the clinical value in staging patients with plasmacytoma (PC) using positron emission tomography (PET).

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.

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.

Although FDG-PET was false negative in 1 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.