Clinical applications of mass spectrometry in multiple myeloma.

Mass spectrometry (MS) is an emerging tool in multiple myeloma that detects and quantifies monoclonal proteins in the peripheral blood with sensitivity several orders of magnitude greater than conventional serum protein electrophoresis and immunofixation. Both intact light-chain (top-down) and clonotypic peptide (bottom-up) MS approaches have demonstrated sensitivity comparable to, or even surpassing, bone marrow (BM)-based assessments using next-generation flow cytometry or sequencing. However, due to the delayed clearance of paraproteins, MS may be less informative for early response assessment, underscoring the need to define the optimal timing for evaluation. MS assays have now transitioned from research settings to commercial availability, addressing the clinical demand for sensitive, noninvasive monitoring tools that avoid reliance on BM biopsies. This review provides an overview of MS and explores its growing role in clinical practice.