Comparison of [18F]fluciclovine and [18F]FDG PET/CT in Newly Diagnosed Multiple Myeloma Patients

Purpose [F-18]FDG PET/CT in multiple myeloma (MM) is currently the best technology to demonstrate patchy and extramedullary disease. However, [F-18]FDG PET has some limitations, and imaging with alternative tracers should be explored. In this study, we aimed to evaluate the performance of [F-18]fluciclovine PET compared to [F-18]FDG PET in newly diagnosed MM patients. Procedures Thirteen newly diagnosed transplant eligible MM patients were imaged both with [F-18]FDG PET/CT and [F-18]fluciclovine PET/CT within 1 week in a prospective study. The subjects were visually assessed positive or negative for disease. The number of lesions and the SUVmax of selected lesions were measured for both tracers. Furthermore, tracer uptake ratios were obtained by dividing lesion SUVmax by blood or bone marrow SUVmax. Between-group differences and correlations were assessed with paired t-tests and Pearson tests. Bone marrow SUVs were compared to bone marrow plasma cell percentage in biopsy samples. Results Nine subjects were assessed positively by [F-18]FDG PET (69%) and 12 positives by [F-18]fluciclovine PET (92%). All positive subjects had [F-18]fluciclovine scans that were qualitatively scored as easier to interpret visually than the [F-18]FDG scans. The number of lesions was also higher; seven of nine subjects with distinct hot spots on [F-18]fluciclovine PET had fewer or no visible lesions on [F-18]FDG PET. The mean lesion SUVmax values were 8.2 and 3.8 for [F-18]fluciclovine and [F-18]FDG, respectively. The mean tumour to blood values were 6.4 and 2.0 for [F-18]fluciclovine and [F-18]FDG, and the mean ratios between tumour and bone marrow were 2.1 and 1.5 for [F-18]fluciclovine and [F-18]FDG. The lesion SUVmax and ratios were significantly higher for [F-18]fluciclovine (all p < 0.01). Local [F-18]fluciclovine SUVmax or SUVmean values in os ilium and the percentage of plasma cells in bone marrow biopsies were linearly correlated (p = 0.048). There were no significant correlations between [F-18]FDG SUVs and plasma cells (p = 0.82). Conclusions Based on this pilot study, [F-18]fluciclovine is a promising tracer for MM. The visual and semi-quantitative evaluations indicate that [F-18]fluciclovine PET/CT can out-perform [F-18]FDG PET/CT at diagnosis.