Abstract
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Objectives: Multiple myeloma (MM) is a hematologic malignancy characterized by accumulation of tumor plasma cells primarily in bone marrow, resulting in renal damage and bone destruction. Smoldering myeloma (SMM) is an asymptomatic precursor to MM, characterized by increased medullar plasma cell infiltration without complications. Assessment of MM and SMM using FDG-PET has thus far been dominated by lesion-based approaches. The aim of this study was to assess the feasibility of measuring global FDG uptake in bone marrow in MM, SMM, and healthy subjects. Methods: Prospective FDG-PET/CT data of 39 MM patients and 8 SMM patients were collected from Odense University Hospital (NCT02187731). Twenty-four healthy control subjects were matched to MM patients by sex and age (±5 years). On a fused PET/CT image, a growing region algorithm with a lower threshold of 150 HU was used to segment bone. A closing algorithm was then applied, allowing the entire bone, including red marrow, to be segmented and quantified. Global SUVmean and global SUVmax, defined as the weighted average of SUVmean and SUVmax respectively according to axial cross-sectional area, were calculated for comparison among the three subject groups. Results: Global SUVmean averages for MM, SMM, and control subjects were 1.71±0.49, 1.27±0.15, and 1.11±0.19, respectively, and global SUVmax averages were 6.13±2.82, 3.70±0.92, and 3.79±1.03, respectively. The global SUVmean of MM patients was significantly increased compared to that of SMM patients (p = 0.017) and that of control subjects (p < 0.001). Global SUVmax also showed a significant difference between MM patients and SMM patients (p = 0.021) as well as between MM patients and control subjects (p < 0.001). Furthermore, the SUVmean of SMM patients was significantly greater than that of control subjects (p = 0.031). No significant difference in SUVmax was observed between SMM and control subjects.
Conclusions: Bone marrow activity in MM, SMM, and healthy subjects as measured using global assessment showed a significant difference in uptake between MM patients and both SMM patients and healthy subjects. Additionally, global SUVmean showed a difference between SMM patients and healthy subjects. Therefore, global SUVmean may reflect the degree of disease activity present in subjects with myeloma disease.