Comparison between 18F-FDG PET/CT and 11C-Choline PET/CT for the evaluation of multiple myeloma

Abstract

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Objectives: Multiple myeloma (MM) is a neoplastic disease involving plasmacells. In more than 40% of patients, litic bone lesions are detected by Whole Body X-Ray (WBXR), and their number is one of the staging parameters in the Durie and Salmon staging system. Some studies suggest that the number of bone lesions could be a prognostic factor. MRI is proven to be more sensitive than WBXR as it can identify early lesions and diffuse infiltrative pattern, but its partial field of view (including only spine and pelvis) is a main limitation. 18F-FDG PET/CT is sensitive for the evaluation of MM but in some cases bone lesions don’t show increased glucose metabolism. Aim of our study was to compare the result of 18F-FDG PET/CT and 11C-Choline in patients with MM, in order to possibly increase PET/CT sensitivity.

Methods: Our population consists of 8 consecutive patients (5M, 2F; mean age 60±6 yo) with biopsy demonstrated MM. Each patient underwent 18F-FDG PET/CT and 11C-Choline PET/CT in a single day. PET/CT scan was carried out with standard procedure and dedicated tomograph. Skull, superior limbs and femurs were included in the field of view. 1 pt was in staging, 1 pt was evaluated after therapy, 6 pts were in re-staging. PET was visually evaluated and considered positive when focal areas of increase uptake were observed on bones.18F-FDG PET/CT results were compared to 11C-Choline PET/CT results in terms of number of lesions detected. PET results were validated by follow-up data and/or other Imaging procedures (MRI, CT, WBXR).

Results: In 5/8 cases FDG PET/CT and Choline PET/CT were superimposable: in 1/5 pts both PET scans showed the same number and location of bone lesions, while in the remaining 4/5 cases FDG and Choline PET were negative. In 3/8 cases FDG PET/CT showed less lesions compared to Choline PET/CT (1 lesion vs 3 lesions in 1 case; 3 lesions vs >10 lesions in one case; 2 lesions vs 7 lesions in the last case). In none of the pts FDG PET/CT showed more lesions compared to Choline.

Conclusions: In our population Choline PET/CT turned out to be more sensitive than 18F-FDG PET/CT for the detection of myelomatous bone lesions. In conclusion, these very preliminary results indicate that Choline PET/CT may be a useful tool contributing to correctly evaluate MM. Further evaluations are needed to understand the uptake mechanism of Choline compared to FDG in pts with MM.