Clinical value of measurable residual disease testing for multiple myeloma and implementation in Japan.

The development of novel therapeutic agents has led to an increase in patients with multiple myeloma (MM) who achieve a complete response (CR). Consequently, a good correlation has been established between the CR rate and progression-free survival, and new methods are needed to stratify CR cases based on the measurable residual disease (MRD) and thus predict prognosis. Previously, multiparameter flow cytometry (MFC), which is rapid and widely available, has been used to assess MRD in patients with MM. Although the EuroFlow next-generation flow method was developed as a highly sensitive and standardized method of MRD detection, the procedure is costly within the current Japanese public medical insurance system. Recently, two Japanese clinical laboratory test companies, SRL and BML, respectively developed new and inexpensive 8- and 10-color single-tube MFC methods intended for the assessment of MRD under the current Japanese public medical insurance system. In this article, I have reviewed the most recent updates on MRD monitoring protocols in Japan and the clinical trials of the use of this parameter in patients with MM.