What is the role of 18F FDG PET scanning in the diagnosis of multiple myeloma?

Updated: Mar 15, 2019
  • Author: Michael E Mulligan, MD; Chief Editor: Felix S Chew, MD, MBA, MEd  more...
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The literature also shows that the use of fluorine-18 fluorodeoxyglucose (18F FDG) positron emission tomography (PET) scanning can be helpful in the staging and posttherapeutic monitoring of multiple myeloma by providing functional detection of high metabolic lesions. [38, 39]   [9, 18, 39, 40, 41] However, a preliminary report by Nanni et al in a small population of patients indicates that carbon-11 (11C)-choline PET scanning may be more sensitive than 18F FDG PET scanning for detecting myeloma lesions. The authors cautioned that more large-scale studies are needed to verify their results. [39]

FDG PET scans that show a lesion with a standardized uptake value (SUV) greater than 11 has been reported to be an indicator of a poorer prognosis. Additionally, patients with 3 or more FDG-avid lesions that do not respond to treatment have poorer outcomes. [40]

In a prospective study of 24 multiple myeloma patients (15 newly diagnosed, 9 pretreated), diffusion-weighted imaging (DWI) was found to be more sensitive than FDG PET in detecting myeloma lesions in a mixed population of primary and pretreated patients, but FDG PET and DWI demonstrated equivalent sensitivities in the subpopulation of primary, untreated patients. [41]

Recognition of a single or serial increase of SUV to 3.5 at a given location, such as within a vertebral body, may help predict an impending pathologic fracture, especially if there is a correlating MRI that shows diffuse vertebral body involvement at the same level. [42]

Because of the small size of many myeloma lesions, PET scans must be carefully evaluated to decrease the number of false negatives. The usual SUV cutoff value of 2.5 does not apply to myeloma lesions that are less than 1 cm in size. For a lesion less than 5 mm, any degree of FDG uptake should be reported as active disease. Lesions between 5 and 10 mm are considered indeterminate.

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