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E1348. Assessment of 11C-Acetate vs. 18 F-Fluorodeoxyglucose as PET Imaging Tracers for the Evaluation of Multiple Myeloma
Authors
  1. Brielle Hentz; The George Washington University School of Medicine and Health Sciences
  2. Murwarit Rahimi; The George Washington University School of Medicine and Health Sciences
  3. Anna Hu; The George Washington University School of Medicine and Health Sciences
  4. Kathleen Johnson; The George Washington University School of Medicine and Health Sciences
  5. Emily Calabria; The George Washington University School of Medicine and Health Sciences
  6. Aneka Khilnani; The George Washington University School of Medicine and Health Sciences
  7. Ramin Javan; The George Washington University School of Medicine and Health Sciences
Background
Multiple Myeloma (MM) is rising in incidence and is associated with significant end organ damage and destructive bone lesions. Consequently, new imaging modalities are of interest to diagnose and improve management and survival rates. Currently, PET/CT is used because of the ability to detect bone lesions and sites of extramedullary involvement. 18 F-fluorodeoxyglucose (18 F-FDG), a glucose analog, is a widely used tracer for detecting increased glycolytic activity in malignant cells and its use with PET is the gold standard imaging modality for patchy and metastatic MM cell distribution. However, a more sensitive tracer is needed to detect early and diffuse bone marrow involvement. 11C-Acetate (11C-ACT) is a novel lipid tracer for MM since tumor cells effectively metabolize acetate and its prominent uptake leads to highly sensitive PET detection. This review evaluates the diagnostic accuracy of 11 C-ACT in the evaluation of MM following treatment in comparison to the established imaging modality, 18 F-FDG.

Educational Goals / Teaching Points
The goal is to assess features of 11 C-ACT PET in evaluating MM. More specifically, to evaluate whether 11 C-ACT PET is more effective than 18 F-FDG PET in assessing progression of tumor burden seen in MM patients.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
PET/CT is a noninvasive imaging technique that enables the visualization of focal lesions using tracers such as FDG and ACT. Tracers can be glucose and lipid analogs that are taken up by metabolically active malignant MM cells and the accumulation of tracers in specific areas enable the easy identification of bone destruction. Whole body PET/CT is important in the diagnosis and staging of MM, and intravenous injections of tracers show functional and anatomic information of the body. Significant 11 C-ACT uptake is seen along with increased tumor burden and higher rate of relapse with a greater number of focal lesions identified. The tracer 11 C-ACT detects diffuse bone marrow involvement due to a positive correlation between its bone marrow uptake and identification of plasma cell infiltrates. The tracer 11 C-ACT exhibits a higher sensitivity of 84.6 compared to 57.5 with 18 F-FDG’s. The maximum standard uptake value (SUVmax) of 11 C-ACT is better for prediction of disease progression and was positively correlated to tumor burden and high risk disease. Also, 11 C-ACT positively identifies patients with focal and diffuse MM and negatively identified patients with asymptomatic MM or precancerous conditions. So 11 C-ACT can potentially be useful over 18 F-FDG for disease staging and confirmation of diagnosis.

Conclusion
MM characterization, treatment monitoring, and risk stratification can be performed more effectively and accurately via lipid metabolism with 11 C-ACT, than through glucose metabolism with 18 F-FDG.