Hexokinase-2 Expression in C-Methionine-Positive, F-FDG-Negative Multiple Myeloma.

PET with F-FDG is the standard modality in nuclear medicine for imaging multiple myeloma (MM). However, viable MM as detected by MRI or PET with other metabolic tracers, including C-methionine, may be missed-for example, because of low hexokinase 2 (HK2) expression of tumor cells. The aim of this study was to further investigate potential reasons for PET false negativity. A cohort of 15 mainly pretreated patients with relapsed or refractory biopsy-proven, serologically active MM who underwent both F-FDG and C-methionine PET/CT was retrospectively analyzed. In 9 of the 15 patients, F-FDG PET was negative in the presence of viable disease. In the remaining 6 patients, both F-FDG and C-methionine PET/CT revealed the same number of MM lesions. At immunohistochemistry, F-FDG-negative myeloma did not exhibit significant differences in HK2 or glucose-6-phosphatase expression from F-FDG-positive disease ( = 0.57 and = 0.44, respectively). Beyond HK2 expression, F-FDG negativity in (mainly pretreated) MM patients seems to be associated with additional causes not yet known.