Answer
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.
-
Lateral radiograph of the skull. This image demonstrates numerous lytic lesions, which are typical for the appearance of widespread myeloma.
-
Lateral radiograph of the lumbar spine. This image shows deformity of the L4 vertebral body that resulted from a plasmacytoma.
-
Radiograph of the right femur. This image demonstrates the typical appearance of a single myeloma lesion as a well-circumscribed lucency in the intertrochanteric region. Smaller lesions are seen at the greater trochanter.
-
Radiograph of the right humerus. This image demonstrates a destructive lesion of the diaphysis. Pathologic fracture is seen.
-
Coronal T1-weighted magnetic resonance image through a myeloma lesion of the humerus. This image shows that the lesion has a low signal intensity. The outer cortical margin is eroded but intact; however, the lesion has transgressed the inner cortex.
-
A T1-weighted magnetic resonance image of the humerus. This image demonstrates a predominantly hypointense to isointense myelomatous lesion in the medullary space of the diaphysis. The lesion extends through the anterior aspect of the cortex.
-
A T2-weighted, fat-suppressed magnetic resonance image of a myeloma lesion of the humerus. This image demonstrates the lesion is hyperintense on this sequence, a typical finding.
-
Anteroposterior radiograph of the left shoulder. This image shows an expansile process in the glenoid.
-
Axial computed tomography (CT) scan of the glenoid. This image shows a well-defined lesion, with the typical CT scan appearance of myeloma. The cortex is intact.
-
Axial computed tomography scan of the glenoid (same patient as in the previous image). One year later, the myeloma lesion had grown significantly, extending to the coracoid process and through the cortex of the glenoid.
-
A T1-weighted magnetic resonance image of the shoulder. This image shows the full extent of myelomatous involvement within the glenoid and coracoid process.
-
A T2-weighted, fat-suppressed magnetic resonance image of the shoulder (same patient as in the previous image). This image demonstrates the myeloma lesion is hyperintense.
-
Axial computed tomography (CT) scan through the left shoulder during a CT-guided biopsy (same patient as in the previous image). This image shows a core biopsy needle has been advanced through the coracoid process to obtain a tissue sample.
