Treatment of multiple myeloma has substantially changed over the past decade with the introduction of several classes of new effective drugs that have greatly improved the rates and depth of response. Response criteria in multiple myeloma were developed to use serum and urine assessment of monoclonal proteins and bone marrow assessment (which is relatively insensitive). Given the high rates of complete response seen in patients with multiple myeloma with new treatment approaches, new response categories need to be defined that can identify responses that are deeper than those conventionally defined as complete response. Recent attempts have focused on the identification of residual tumour cells in the bone marrow using flow cytometry or gene sequencing. Furthermore, sensitive imaging techniques can be used to detect the presence of residual disease outside of the bone marrow. Combining these new methods, the International Myeloma Working Group has defined new response categories of minimal residual disease negativity, with or without imaging-based absence of extramedullary disease, to allow uniform reporting within and outside clinical trials. In this Review, we clarify several aspects of disease response assessment, along with endpoints for clinical trials, and highlight future directions for disease response assessments.
Prof Shaji Kumar, Bruno Paiva, PhD, Prof Kenneth C Anderson, MD, Prof Brian Durie, MD, Ola Landgren, MD, Prof Philippe Moreau, MD, Prof Nikhil Munshi, MD, Sagar Lonial, MD, Prof Joan Bladé, MD, Prof Maria-Victoria Mateos, MD, Meletios Dimopoulos, Prof MD, Efstathios Kastritis, MD, Prof Mario Boccadoro, MD, Prof Robert Orlowski, MD, Prof Hartmut Goldschmidt, MD, Prof Andrew Spencer, MD, Prof Jian Hou, MD, Prof Wee Joo Chng, MD, Saad Z Usmani, MD, Elena Zamagni, MD, Prof Kazuyuki Shimizu, MD, Prof Sundar Jagannath, MD, Prof Hans E Johnsen, MD, Evangelos Terpos, MD, Prof Anthony Reiman, MD, Prof Robert A Kyle, MD, Prof Pieter Sonneveld, MD, Prof Paul G Richardson, MD, Prof Philip McCarthy, MD, Prof Heinz Ludwig, MD, Prof Wenming Chen, MD, Prof Michele Cavo, MD, Prof Jean-Luc Harousseau, MD, Prof Suzanne Lentzsch, MD, Jens Hillengass, MD, Prof Antonio Palumbo, MD, Prof Alberto Orfao, PhD, Prof S Vincent Rajkumar, MD, Prof Jesus San Miguel, MD, Prof Herve Avet-Loiseau, MD