Abstract
Staging of patients with myeloma currently takes into account the number of bone lesions identified with standard X-rays. Magnetic Resonance Imaging (MRI) appears to be a more sensitive imaging technique in patients with multiple myeloma (MM) but it is not adapted to the investigation of the entire skeleton. Positron Emission Tomography (PET) imaging appears promising but this approach remains to be validated in patients with MM. Most patients with neoplasia have been performed with 18F-2-deoxy-D-glucose (FDG), a functional marker suggested to identify “active” tumor sites and useful to assess bone or extra-osseous tissue. Conversely Na18F binding is strictly limited to bone. To determine the potential usefulness of these two markers we performed a comparative analysis of these two imaging techniques in patients with MM.
Nine patients with progressive MM, including bone lesions, underwent x-ray imaging, MRI, 18FDG and Na18F scanning. Both PET scans were performed within a one-week time frame in each patient. The number and localizations of suspect lesions identified by each type of imaging technique was assessed independently then compared. 18FDG and Na18F data were compared to X-ray/MRI data for skull, spine, pelvis and femur/humerus localizations. Localizations were considered positive in case of increased fixation with 18FDG or increased or decreased fixation with Na18F.
Comparison of FDG data with X-ray/MRI showed that FDG allowed the detection of only 3 of 35 types of localizations identified by X-ray/MRI, whatever the localization (skull, femur/humerus, spine and pelvis) observed on X-ray/MRI. 18FDG showed three lesions which had not been identified by X-ray/MRI, as well as 8 costal localizations and 1 extra-osseous localization. Comparison of Na18F data with X-ray/MRI showed that Na18F allowed the detection of 17 of 35 types of localizations. In particular, Na18F identified 13 of the 19 spinal localizations observed with x-ray/MRI but only 2 of 9 skull lesions. Na18F identified 11 localizations which had not been identified by X-ray/MRI. Furthermore Na18F also identified costal localizations in all patients. Qualitative analysis of PET scans showed that background was significantly lower with Na18F imaging than with 18FDG imaging. In conclusion 18FDG and Na18F provide significantly different results in patients with progressive MM. 18FDG imaging was poorly correlated with X-rayMRI while Na18F imaging was particularly useful to identify costal and spinal lesions. PET scan could be a useful method in the staging of MM patients at diagnosis or to determine response.
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