Comparison of 11C-4′-thiothymidine, 11C-methionine, and 18F-FDG PET/CT for the detection of active lesions of multiple myeloma

Abstract

Purpose: The aims of this study were to evaluate the possibility of using 11C-methionine (11C-MET) and 11C-4′-thiothymidine (11C-4DST) whole-body PET/CT for the imaging of amino acid metabolism and DNA synthesis, respectively, when searching for bone marrow involvement in patients with multiple myeloma (MM) and to compare these findings with those for 18F-FDG PET/CT and aspiration cytology. Methods: A total of 64 patients with MM, solitary plasmacytoma, monoclonal gammopathy of undetermined significance, or an unspecified diagnosis were prospectively enrolled. All the patients underwent three whole-body PET/CT examinations within a period of 1 week. First, the tracer accumulation was visually evaluated as positive, equivocal, or negative for 55 focal lytic lesions visualized using CT in 24 patients. Second, the percentages of marrow plasma cells as calculated using a bone marrow aspiration smear and tracer accumulation were evaluated in the posterior iliac crests of 36 patients. Results: Among the 55 lytic lesions, the 11C-MET and 11C-4DST findings tended to reveal more positive findings than the 18F-FDG findings. Based on the standard criteria for the diagnosis of active myeloma using the percentage of marrow plasma cells, significant differences were found between the 18F-FDG and 11C-MET findings and between the 18F-FDG and 11C-4DST findings, but no significant difference was observed between the 11C-MET and 11C-4DST findings. Conclusion: The addition of 11C-MET and 11C-4DST to 18F-FDG when performing PET/CT enabled clearer evaluations of equivocal lesions. Based on cytological diagnostic criteria, 11C-MET and 11C-4DST were more sensitive than 18F-FDG for the detection of active lesions. 11C-MET and 11C-4DST were more useful than 18F-FDG for the detection of active lesions, especially during the early stage of disease.