Objective: To determine abdominal adipose tissue parameters on PET/CT in patients with monoclonal gammopathy of undetermined significance (MGUS) and multiple myeloma (MM) that may serve as predictors of progression of MGUS to MM. We hypothesized that patients with MM had higher abdominal adiposity and higher fat metabolic activity compared to patients with MGUS.
Materials and methods: Our retrospective study was IRB approved and HIPAA compliant. The study group comprised 40 patients (mean age 64 ± 13 years) with MGUS and 32 patients (mean age 62 ± 10 years) with recently diagnosed MM (mean time since diagnosis of MM 3.0 ± 3.9 months) who had not undergone MM treatment. All patients underwent whole body FDG-PET/CT. Total abdominal adipose tissue (TAT), abdominal subcutaneous adipose tissue (SAT) and visceral adipose tissue (VAT) cross sectional areas (CSA) (cm(2)) and metabolic activity (SUV) were assessed. Groups were compared using ANOVA. ROC curve analysis was performed to determine cutoff values for abdominal adipose tissue parameters to detect MM.
Results: Patients with recently diagnosed MM had higher TAT and SAT CSA (p ≤ 0.03) and higher fat metabolic activity (p < 0.01). VAT metabolic activity showed the highest sensitivity and specificity for identifying patients with MM (area under the curve 0.95 with cutoff value of >0.34, sensitivity 90.6 %, specificity 92.5 %, p < 0.0001).
Conclusions: Patients who were recently diagnosed with MM had higher abdominal fat CSA and higher fat metabolic activity compared to patients with MGUS. These parameters may serve as novel biomarkers of progression of MGUS to MM.
Keywords: Abdominal adiposity; FDG-PET/CT; MGUS; Multiple myeloma.