The response of patients with multiple myeloma (MM) to therapy is always variable. Speaking from the 23rd Congress of the European Hematological Association (EHA) 2018, held in Stockholm, Sweden, Shaji Kumar, MD, of the Mayo Clinic, Rochester, MN, explains why an immediate and strong response to therapy isnt always the best outcome to hope for, and mentions the factors that can have an impact on the efficacy of some drugs, from the biology of the disease to patient fitness.