Diagnostic utility of FDG PET in multiple myeloma

Objective: Very little information is available regarding the diagnostic utility of positron emission tomography with [F-18]fluorodeoxyglucose (FDG PET) in multiple myeloma. Our objective was to further define the role of FDG PET in the clinical assessment of patients with multiple myeloma. Design and patients: Nine whole-body PET scans (45 min after intravenous administration of 370-555 MBq FDG) were performed in six patients (age 38-62 years, 5 males) with multiple myeloma for evaluation of the extent of disease at the time of initial diagnosis (n=3) and for assessment of therapy response (n=3). Three patients had PET scans both before and after therapy. Prior treatments included chemoradiation therapy (n=2) and chemotherapy with autologous bone marrow transplantation (n=1). Correlative imaging data were available in all patients and included skeletal radiographic survey (n=6), bone scan (n=3), and spinal CT or MRI (n=4), and were all obtained within 3 months of the PET study. Validation was by clinical or imaging follow-up. Results: In three patients with both pre- and post-therapy PET scans, PET demonstrated a favorable treatment response, by showing a decline in lesion metabolic activity (n=1), or progression of disease, by showing development of new lesions or higher lesion glucose metabolism (n=2), concordant with the clinical evaluation, while the other imaging studies showed no discernible interval changes. PET detected multiple hypermetabolic lesions in one patient with a negative bone scan and concordant positive skeletal radiographic survey. Bone scans underestimated the extent of disease in two other patients in comparison with PET. PET also detected a few early marrow lesions with subtle radiographic changes while all radiographically aggressive lytic lesions corresponded to intense hypermetabolism on PET. Conclusion: PET can detect early marrow involvement of multiple myeloma and is useful in assessing the extent of active disease at the time of initial presentation and in evaluating treatment response.