18F-FDG-PET/CT and Osteolytic Bone Disease in Multiple Myeloma

Introduction: FDG-PET/CT is a promising methodology for staging, prognostication, and response evaluation in multiple myeloma (MM). The number of focal FDG lesions and the intensity of FDG uptake (standard uptake value, SUV) at diagnosis are informative of disease aggressiveness. Osteolytic bone disease is a hallmark of MM. Hypothetically; increased focal metabolic activity will precede, induce and correlate to osteolytic lesions. We aimed to elucidate the association between focal FDG positive lesions and osteolytic bone disease in MM patients.

Methods: Twenty-two newly diagnosed MM patients, 16 males and 6 females aged 53-81years, were prospectively enrolled and studied with a standardized baseline FDG-PET/CT at diagnosis. A nuclear medicine and a radiology specialist evaluated the PET and CT parts separately and independently. Focal FDG positive lesions were assessed by dedicated software (ROVER™, ABX, Germany) to yield volume and SUV measures. All osteolytic lesions identified on CT were noted by size and localization.

Results: FDG-PET and CT together identified a total of 390 lesions. We found more osteolytic lesions on CT (335) than FDG-positive lesions (169); the concordance between the modalities was 30%. 34% (114/335) of lytic lesions were FDG-positive, whereas ⅔ (114/169) of focal FDG-PET positive lesions were lytic according to CT. We found a significant correlation between higher FDG uptake measured as SUVpeak and osteolytic lesions >10 mm, and focal lesions with high FDG uptake had more pronounced osteolysis than focal lesions with less FDG uptake. Still sparse follow-up data did not allow analysis of the predictive value of focal PET positivity and the risk of development of future osteolysis. More compulsive data will be presented at the meeting.

Conclusion: FDG-PET/CT offers dual information including metabolic activity (FDG-avidity) and degree of lytic bone disease (low dose whole body CT) in MM. About ⅔ (221/335) of osteolytic lesions were FDG-negative, whereas ⅔ (114/169) of FDG-positive lesions had a lytic component.