Role of Imaging in the Evaluation of Minimal Residual Disease in Multiple Myeloma Patients

The International Myeloma Working Group (IMWG) recently introduced the evaluation of minimal residual disease (MRD) within the multiple myeloma (MM) response criteria, and MRD negativity assessed inside and outside the bone marrow is currently considered the most powerful predictor of favorable long-term outcomes. However, MRD evaluation has thus far relied on flow-cytometry or molecular-based methods, despite the limitations associated with the patchy infiltration of bone marrow (BM) plasma cells and the presence of extra-medullary (EMD). On the contrary, imaging-based sensitive response assessment through the use of functional rather than morphological whole-body (WB) imaging techniques, such as positron emission tomography with computed tomography (PET/CT) and magnetic resonance imaging (MRI), likely is a promising strategy to overcome these limitations in evaluating response to therapy and in the assessment of the MRD status in MM patients. However, despite the significant advances in the development and availability of novel functional imaging techniques for MRD evaluation, a worldwide standardization of imaging criteria for acquisition, interpretation, and reporting is yet to be determined and will be object of future investigations