Intensifying treatment in PET-positive multiple myeloma patients after upfront autologous stem cell transplantation.

18F-Fluorodeoxyglucose positron emission tomography/computed tomography (PET) positivity after first-line treatment with autologous stem cell transplantation (ASCT) in multiple myeloma is strongly correlated with reduced progression-free and overall survival. However, PET-positive patients who achieve PET negativity after treatment seem to have comparable outcomes to patients who were PET negative at diagnosis. Hence, giving PET-positive patients additional treatment may improve their outcome. In this phase II study, we screened first-line patients with very good partial response (VGPR) or better after ASCT with PET. PET-positive patients received four 28-day cycles of carfilzomib-lenalidomide-dexamethasone (KRd). Flow cytometry-based minimal residual disease (MRD) analysis was performed before and after treatment for correlation with PET. Overall, 159 patients were screened with PET. A total of 53 patients (33%) were PET positive and 57% of PET-positive patients were MRD negative, demonstrating that these response assessments are complementary. KRd consolidation converted 33% of PET-positive patients into PET negativity. MRD-negative patients were more likely to convert than MRD-positive patients. In summary, PET after ASCT detected residual disease in a substantial proportion of patients in VGPR or better, even in patients who were MRD negative, and KRd consolidation treatment changed PET status in 33% of patients.

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

PURPOSE: [18F]FDG PET/CT in multiple myeloma (MM) is currently the best technology to demonstrate patchy and extramedullary disease. However, [18F]FDG PET has some limitations, and imaging with alternative tracers should be explored. In this study, we aimed to evaluate the performance of [18F]fluciclovine PET compared to [18F]FDG PET in newly diagnosed MM patients. PROCEDURES: Thirteen newly diagnosed transplant eligible MM patients were imaged both with [18F]FDG PET/CT and [18F]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 [18F]FDG PET (69%) and 12 positives by [18F]fluciclovine PET (92%). All positive subjects had [18F]fluciclovine scans that were qualitatively scored as easier to interpret visually than the [18F]FDG scans. The number of lesions was also higher; seven of nine subjects with distinct hot spots on [18F]fluciclovine PET had fewer or no visible lesions on [18F]FDG PET. The mean lesion SUVmax values were 8.2 and 3.8 for [18F]fluciclovine and [18F]FDG, respectively. The mean tumour to blood values were 6.4 and 2.0 for [18F]fluciclovine and [18F]FDG, and the mean ratios between tumour and bone marrow were 2.1 and 1.5 for [18F]fluciclovine and [18F]FDG. The lesion SUVmax and ratios were significantly higher for [18F]fluciclovine (all p < 0.01). Local [18F]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 [18F]FDG SUVs and plasma cells (p = 0.82). CONCLUSIONS: Based on this pilot study, [18F]fluciclovine is a promising tracer for MM. The visual and semi-quantitative evaluations indicate that [18F]fluciclovine PET/CT can out-perform [18F]FDG PET/CT at diagnosis.