18F-fluorocholine versus 18F-fluorodeoxyglucose for PET/CT imaging in patients with suspected relapsing or progressive multiple myeloma: a pilot study.

PURPOSE

Hybrid positron emission tomography/computed tomography (PET/CT) has now become available, as well as whole-body, low-dose multidetector row computed tomography (MDCT) or magnetic resonance imaging (MRI). The radioactive glucose analogue 18F-fluorodeoxyglucose (FDG) is the most widely used tracer but has a relatively low sensitivity in detecting multiple myeloma (MM). We compared FDG with a more recent metabolic tracer, 18F-fluorocholine (FCH), for the detection of MM lesions at time of disease relapse or progression.

METHODS

We analyzed the results of FDG and FCH imaging in 21 MM patients undergoing PET/CT for suspected relapsing or progressive MM. For each patient and each tracer, an on-site reader and a masked reader independently determined the number of intraosseous and extraosseous foci of tracer and the intensity of uptake as measured by their SUVmax and the corresponding target/non-target ratio (T/NT).

RESULTS

In the skeleton of 21 patients, no foci were found for two cases, uncountable foci were observed in four patients, including some mismatched FCH/FDG foci. In the 15 patients with countable bone foci, the on-site reader detected 72 FDG foci vs. 127 FCH foci (+76 %), whereas the masked reader detected 69 FDG foci vs. 121 FCH foci (+75 %), both differences being significant. Interobserver agreement on the total number of bone foci was very high, with a kappa coefficient of 0.81 for FDG and 0.89 for FCH. Measurement of uptake in the matched foci that took up both tracers revealed a significantly higher median SUVmax and T/NT for FCH vs. FDG. Almost all unmatched foci were FCH-positive FDG-negative (57/59 = 97 % on-site and 56/60 = 93 % on masked reading); they were more frequently observed than matched foci in the head and neck region.

CONCLUSIONS

These findings suggest that PET/CT performed for suspected relapsing or progressive MM would reveal more lesions when using FCH rather than FDG.