Assessment of glucose metabolism and cellular proliferation in multiple myeloma: a first report on combined 18F-FDG and 18F-FLT PET/CT imaging

C Sachpekidis,H Goldschmidt,A Kopp-Schneider,A Dimitrakopoulou-Strauss,K Kopka

doi:10.1186/s13550-018-0383-7

Abstract

BackgroundDespite the significant upgrading in recent years of the role of 18F-FDG PET/CT in multiple myeloma (MM) diagnostics, there is a still unmet need for myeloma-specific radiotracers. 3′-Deoxy-3′-[18F]fluorothymidine (18F-FLT) is the most studied cellular proliferation PET agent, considered a potentially new myeloma functional imaging tracer. The aim of this pilot study was to evaluate 18F-FLT PET/CT in imaging of MM patients, in the context of its combined use with 18F-FDG PET/CT.ResultsEight patients, four suffering from symptomatic MM and four suffering from smoldering MM (SMM), were enrolled in the study. All patients underwent 18F-FDG PET/CT and 18F-FLT PET/CT imaging by means of static (whole body) and dynamic PET/CT of the lower abdomen and pelvis (dPET/CT) in two consecutive days. The evaluation of PET/CT studies was based on qualitative evaluation, semi-quantitative (SUV) calculation, and quantitative analysis based on two-tissue compartment modeling. 18F-FDG PET/CT demonstrated focal, 18F-FDG avid, MM-indicative bone marrow lesions in five patients. In contrary, 18F-FLT PET/CT showed focal, 18F-FLT avid, myeloma-indicative lesions in only two patients. In total, 48 18F-FDG avid, focal, MM-indicative lesions were detected with 18F-FDG PET/CT, while 17 18F-FLT avid, focal, MM-indicative lesions were detected with 18F-FLT PET/CT. The number of myeloma-indicative lesions was significantly higher for 18F-FDG PET/CT than for 18F-FLT PET/CT. A common finding was a mismatch of focally increased 18F-FDG uptake and reduced 18F-FLT uptake (lower than the surrounding bone marrow). Moreover, 18F-FLT PET/CT was characterized by high background activity in the bone marrow compartment, further complicating the evaluation of bone marrow lesions. Semi-quantitative evaluation revealed that both SUVmean and SUVmax were significantly higher for 18F-FLT than for 18F-FDG in both MM lesions and reference tissue. SUV values were higher in MM lesions than in reference bone marrow for both tracers.ConclusionsDespite the limited number of patients analyzed in this pilot study, the first results of the trial indicate that 18F-FLT does not seem suitable as a single tracer in MM diagnostics. Further studies with a larger patient population are warranted to generalize the herein presented results.

Highlights

Despite the significant upgrading in recent years of the role of 18F-FDG PET/CT in multiple myeloma (MM) diagnostics, there is a still unmet need for myeloma-specific radiotracers. 3′-Deoxy-3′-[18F]fluorothymidine (18F-FLT) is the most studied cellular proliferation PET agent, considered a potentially new myeloma functional imaging tracer
Despite the limited number of patients analyzed in this pilot study, the first results of the trial indicate that 18F-FLT does not seem suitable as a single tracer in MM diagnostics
PET/CT in imaging of MM patients, in the context of its combined use with 18F-FDG PET/CT. If it were used as the only functional imaging modality, 18F-FLT PET/CT would have characterized only two patients as demonstrating myeloma-associated, skeletal manifestations

Summary

Introduction

Despite the significant upgrading in recent years of the role of 18F-FDG PET/CT in multiple myeloma (MM) diagnostics, there is a still unmet need for myeloma-specific radiotracers. 3′-Deoxy-3′-[18F]fluorothymidine (18F-FLT) is the most studied cellular proliferation PET agent, considered a potentially new myeloma functional imaging tracer. There has been an increasing interest over the past few years regarding the role of imaging in multiple myeloma (MM) This interest has been driven by the considerable technological advances, mostly in cross sectional imaging, that have taken place and by the recent introduction of some very effective novel therapeutic agents in the oncologist’s armamentarium, which have led to unparalleled levels of response in the disease. In this context, the role of molecular imaging with PET has gained significant importance in MM. The International Myeloma Working Group (IMWG) has recommended the use of 18F-FDG PET/CT as a diagnostic tool in patients with active MM, smoldering MM (SMM), and solitary plasmacytoma [7]

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