11C-Acetate PET/CT for Metabolic Characterization of Multiple Myeloma: A Comparative Study with 18F-FDG PET/CT

We prospectively compared C-11-acetate with F-18-FDG in a PET/CT evaluation of multiple myeloma (MM), specifically on diagnostic accuracy, identification of high-risk patients, and monitoring of treatment response. Methods: Dual-tracer PET/CT was performed on 35 pathologically and clinically confirmed and untreated patients (26 with symptomatic MM, 5 with smoldering MM, and 4 with monoclonal gammopathy of unknown significance) and 20 individuals with normal marrow. Results: C-11-acetate showed significant incremental value over F-18-FDG (84.6% vs. 57.7%) for positively identifying patients with diffuse and focal symptomatic MM, and was negative in patients with indolent smoldering MM and monoclonal gammopathy of unknown significance. Three functional parameters-number of C-11-acetate- avid and F-18-FDG-avid focal bone lesions and C-11-acetate general marrow activity-strongly correlated with beta-2-microglobulin as surrogate imaging markers of tumor burden. After induction chemotherapy, the metabolic change in C-11- acetate general marrow activity correlated with clinical response. Conclusion: Metabolic characterization of MM in diagnosis, risk stratification, and treatment monitoring can be done more accurately by assessing lipid metabolism with C-11- acetate than by assessing glucose metabolism with F-18-FDG.