Role of 18F-FDG PET/CT in the assessment of bone involvement in newly diagnosed multiple myeloma:: preliminary results

Purpose: Multiple myeloma ( MM) is a malignant B cell and plasma cell disorder which involves the skeleton in more than 80% of patients at diagnosis. The aim of this study was to compare whole-body X-ray (WBXR), MRI and F-18-FDG PET/CT in patients with MM. Methods: The study population comprised 28 newly diagnosed MM patients. Findings of F-18-FDG PET/CT were compared with those of WBXR and MRI with regard to the number and site of lesions detected. Results: Comparing F-18-FDG PET/CT and WBXR, it was found that in 16/28 pts (57%) F-18-FDG PET/CT detected more lesions, all of which were located in the skeleton. Nine of these 16 patients had a completely negative WBXR survey. In 12/28 pts (43%) the two methods yielded equivalent findings. Comparing F-18-FDG PET/CT and MRI, it was found that in 7/28 pts ( 25%), F-18-FDG PET/CT detected more lytic bone lesions, all of which were located outside the field of view of MRI ( bone lesions in six cases and a soft tissue lesion in one). In 14/28 ( 50%), F-18-FDG PET/CT and MRI detected the same number of lesions in the spine and pelvis, while in 7/28 ( 25%) MRI detected an infiltrative pattern in the spine whereas F-18-FDG PET/CT was negative. Conclusion: F-18-FDG PET/CTappears to be more sensitive than WBXR for the detection of small lytic bone lesions, whereas it has the same sensitivity as MRI in detecting bone disease of the spine and pelvis. On the other hand, MRI may be superior to F-18-FDG PET/CT in diagnosing an infiltrative pattern in the spine. Therefore, careful evaluation of MM bone disease at diagnosis should include both MRI of the spine and F-18-FDG PET/CT.