Challenges and opportunities in the assessment of measurable residual disease in multiple myeloma.

Treatment response assessment in multiple myeloma (MM) relies on the detection of paraprotein in serum and/or urine, bone marrow morphology and immunohistochemistry. With remarkable advances in therapy, particularly in the newly diagnosed setting, achievement of complete remission became frequent, creating the need to identify smaller amounts of residual disease and understand their prognostic and therapeutic implications. Measurable residual disease (MRD) can be assessed primarily by flow cytometry and next generation sequencing and state-of-the-art assays have sensitivity approaching 1 in 106 cells. This review discusses the existing challenges in utilizing MRD to inform management of MM and highlights open research questions and opportunities as MRD is more routinely incorporated into clinical practice for patients with MM.