Meta-analysis of whole-body MRI versus FDG PET/CT to assess treatment response in MM may suggest a complementary benefit when utilizing both modalities.
Response to therapy in patients with multiple myeloma (MM) is assessed according to the International Myeloma Working Group’s uniform response criteria. These criteria include the following categories: stringent complete response, complete response, minimal residual disease, very good partial response, partial response, stable disease, and progressive disease, which are based on measurements of 24-hour urinary M protein, serum M protein, and serum free light chain protein. Although as many as half of patients will achieve a complete response with therapy, most patients will relapse, and current treatment response methods have low sensitivity for residual disease. Recent studies highlight the utility of imaging methods using whole-body MRI, with an emphasis on diffusion-weighted imaging (DWI), or FDG PET/CT to assess treatment response, both of which are now included in the latest consensus criteria. Sharath Rama and colleagues reported findings from a systematic review aimed at assessing the diagnostic accuracy of whole-body MRI and FDG PET/CT for MM treatment response assessment.
Twelve studies of 373 patients were included in the analysis, all of which used whole-body MRI or FDG PET/CT to evaluate MM treatment response. Six studies evaluated both methods, 4 used only whole-body MRI, 2 used only FDG PET/CT, and 5 studies of MRI included DWI. Pooled sensitivity for whole-body MRI was 87% (95% confidence interval [CI], 75%-93%) versus 64% (95% CI, 45%-79%) for FDG PET/CT, while pooled specificity for whole-body MRI was 57% (95% CI, 37%-76%) versus 82% (95% CI, 75%-88%) for FDG PET/CT (sensitivity, P = .29; specificity, P = .01). For studies that evaluated both modalities directly, specificity was 90% (95% CI, 80%-100%) versus 66% (95% CI, 47%-85%), and sensitivity was 56% (95% CI, 44%-68%) versus 81% (95% CI, 72%-90%) with whole-body MRI and FDG PET/CT, respectively (sensitivity, P = .18; specificity, P <.001). For MRI with DWI, sensitivity and specificity were 93% (95% CI, 75%-98%) and 57% (95% CI, 21%-87%), respectively, versus 74% (95% CI, 60-85%) and 56% (95% CI, 38-73%), respectively, for whole-body MRI without DWI (sensitivity, P = .27; specificity, P = .99).
Overall, FDG PET/CT demonstrated superior specificity over whole-body MRI. Although whole-body MRI demonstrated higher sensitivity, this difference was not significant and may have contributed to the high sensitivity of DWI. Based on this meta-analysis, there may be a role for complementary use of whole-body MRI and FDG PET/CT in assessment of MM treatment response; however, further studies are needed to confirm this relationship.
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