Dynamic monitoring of myeloma minimal residual disease with targeted mass spectrometry

Minimal residual disease (MRD) assessment has been established as a prognostic indicator for multiple myeloma (MM) [ 1 ]. MRD-negativity correlates with longer progression-free survival and has the potential to become a surrogate endpoint in future clinical trials [ 2 , 3 ]. Current methods used in clinical trials for MRD detection, such as next-generation sequencing (NGS) and flow cytometry, are sensitive enough to detect one myeloma cell in ≥ 10 5 cells in bone marrow [ 4 ]. However, the invasive character of bone marrow aspiration and the heterogeneous distribution of myeloma cells limits the application [ 5 ]. For monitoring the monoclonal protein (M-protein) in blood, methods such as serum protein electrophoresis (SPEP) and free light chain (FLC) analysis remain the gold standard. However, these electrophoretic methods are not sensitive enough to detect low disease burden in patients with stringent complete remission.