Prospective Evaluation of Whole-Body MRI versus FDG PET/CT for Lesion Detection in Participants with Myeloma

Purpose: To compare disease detection of myeloma using contemporary whole-body (WB) MRI and fluorine 18 (F-18) fluorodeoxyglucose (FDG) PET/CT protocols and to correlate imaging with laboratory estimates of disease burden, including molecular characteristics. Materials and Methods: In this observational, prospective study, participants were recruited from November 2015 to March 2018 who had a diagnosis of myeloma, who were planned to undergo chemotherapy and autologous stem cell transplantation, and who underwent baseline WB-MRI and FDG PET/CT (ClinicalTrials.gov identifier NCT02403102). Baseline clinical data, including genetics, were collected. Paired methods were used to compare burden and patterns of disease. Results: Sixty participants (mean age, 60 years +/- 9 [standard deviation]; 35 men) underwent baseline WB-MRI and FDG PET/CT. WB-MRI showed significantly higher detection for focal lesions at all anatomic sites (except ribs, scapulae, and clavicles) and for diffuse disease at all sites. Two participants presented with two or more focal lesions smaller than 5 mm only at WB-MRI but not FDG PET/CT. Participants with diffuse disease at MRI had higher plasma cell infiltration (percentage of nucleated cells: median, 60% [interquartile range {IQR}, 50%-61%] vs 15% [IQR, 4%-50%]; P =.03) and paraprotein levels (median, 32.0 g/L [IQR, 24.0-48.0 g/L] vs 20.0 g/L [IQR, 12.0-22.6 g/L]; P =.02) compared with those without diffuse disease. All genetically high-risk tumors showed diffuse infiltration at WB-MRI. Conclusion: WB-MRI helped detect a higher number of myeloma lesions than FDG PET/CT, and diffuse disease detected at WB-MRI correlated with laboratory measures of disease burden and molecular markers of risk.