Characterization of Bone Lesions in Myeloma Before and During Anticancer Therapy Using 18F-FDG-PET/CT and 18F-NaF-PET/CT.

BACKGROUND: The objective of this study was to characterize tumor activity and mineralization status in newly-detected multiple myeloma (MM) bone lesions using 2-18F-fluoro-2-deoxy-D-glucose (18F-FDG)-PET/CT and 18F-sodium fluoride (18F-NaF)-PET/CT before and after antitumor treatment. MATERIALS AND METHODS: In this retrospective study, seven patients with histologically-verified MM were included (four women, three men; median age=57 years, standard deviation=11.23 years). PET/CT was performed with 18F-FDG and with 18F-NaF, both at baseline and after treatment. All patients had positive scans. Volumes of interest (VOIs) were drawn over all 18F-FDG-PET/CT-positive bone lesions, as well as the corresponding regions in 18F-NaF-PET/CT. For characterization of bone lesions, semi-quantitative standard uptake value (SUV) parameters were measured. RESULTS: 18F-FDG-PET/CT in the seven patients detected 39 metabolically active lesions that were correlated with the corresponding sites in 18F-fluoride-PET/CT. Overall, the lesions showed a response to therapy, with a significant decrease in SUVmax on PET/CT using 18F-FDG (p<0.001) and with 18F-NaF (p<0.001). In four patients with a second follow-up scan (at a median of 17 months after baseline scan), there was no significant change in lesion uptake. CONCLUSION: Based on our data, antitumor therapy in MM reduces not only tumor activity, but also the mineralization status of bone lesions. A second follow-up scan in a subset of the cohort yielded no change in mineralization status.

Association Between Osteogenesis and Inflammation During the Progression of Calcified Plaque Evaluated by 18F-Fluoride and 18F-FDG.

18F-FDG is the most widely validated PET tracer for the evaluation of atherosclerotic inflammation. Recently, 18F-NaF has also been considered a potential novel biomarker of osteogenesis in atherosclerosis. We aimed to analyze the association between inflammation and osteogenesis at different stages of atherosclerosis, as well as the interrelationship between these 2 processes during disease progression. Methods: Thirty-four myeloma patients underwent 18F-NaF and 18F-FDG PET/CT examinations. Lesions were divided into 3 groups (noncalcified, mildly calcified, and severely calcified lesions) on the basis of calcium density as measured in Hounsfield units by CT. Tissue-to-background ratios were determined from PET for both tracers. The association between inflammation and osteogenesis during atherosclerosis progression was evaluated in 19 patients who had at least 2 examinations with both tracers. Results: There were significant correlations between the maximum tissue-to-background ratios of the 2 tracers (Spearman r = 0.5 [P < 0.01]; Pearson r = 0.4 [P < 0.01]) in the 221 lesions at baseline. The highest uptake of both tracers was observed in noncalcified lesions, but without any correlation between the tracers (Pearson r = 0.06; P = 0.76). Compared with noncalcified plaques, mildly calcified plaques showed concordant significantly lower accumulation, with good correlation between the tracers (Pearson r = 0.7; P < 0.01). In addition, enhanced osteogenesis-derived 18F-NaF uptake and regressive inflammation-derived 18F-FDG uptake were observed in severely calcified lesions (Pearson r = 0.4; P < 0.01). During follow-up, increased calcium density and increased mean 18F-NaF uptake were observed, whereas mean 18F-FDG uptake decreased. Most noncalcified (86%) and mildly calcified (81%) lesions and 47% of severely calcified lesions had concordant development of both vascular inflammation and osteogenesis. Conclusion: The combination of 18F-NaF PET imaging and 18F-FDG PET imaging promotes an understanding of the mechanism of plaque progression, thereby providing new insights into plaque stabilization.