[Treatment strategy for relapsed or refractory myeloma according to the new Guidelines].

The development of novel agents for treating multiple myeloma (MM) has markedly improved the treatment outcome and has caused a major paradigm shift in treatment strategies. In Japan, bortezomib and lenalidomide have been approved for the initial treatment; additionally, seven novel drugs, including next-generation proteasome inhibitors, immunomodulatory drugs, histone deacetylase inhibitors, and monoclonal antibodies, have been approved for relapsed and/or refractory MM treatment. Of these novel agents, daratumumab-containing regimens have been reported to induce a deep response, such as minimal residual disease-negative status, even in relapsed patients. Thus, compared with the initial therapy, many efficacious choices are available for treatment at the time of MM relapse; and salvage therapy is currently considered to be the most important treatment strategy for MM. In clinical practice, it is desirable to consider patient, disease, and therapeutic factors to make an optimal treatment decision for each patient.