PURPOSE: The existence of patients with multiple myeloma (MM) and light-chain (AL) amyloidosis who present with a monoclonal gammopathy of undetermined significance (MGUS)-like phenotype has been hypothesized, but methods to identify this subgroup are not standardized and its clinical significance is not properly validated. PATIENTS AND METHODS: An algorithm to identify patients having MGUS-like phenotype was developed on the basis of the percentages of total bone marrow (BM) plasma cells (PC) and of clonal PC within the BM PC compartment, determined at diagnosis using flow cytometry in 548 patients with MGUS and 2,011 patients with active MM. The clinical significance of the algorithm was tested and validated in 488 patients with smoldering MM, 3,870 patients with active MM and 211 patients with AL amyloidosis. RESULTS: Patients with smoldering MM with MGUS-like phenotype showed significantly lower rates of disease progression (4.5% and 0% at 2 years in two independent series). There were no statistically significant differences in time to progression between treatment versus observation in these patients. In active newly diagnosed MM, MGUS-like phenotype retained independent prognostic value in multivariate analyses of progression-free survival (PFS; hazard ratio [HR], 0.49; P = .001) and overall survival (OS; HR, 0.56; P = .039), together with International Staging System, lactate dehydrogenase, cytogenetic risk, transplant eligibility, and complete remission status. Transplant-eligible patients with active MM with MGUS-like phenotype showed PFS and OS rates at 5 years of 79% and 96%, respectively. In this subgroup, there were no differences in PFS and OS according to complete remission and measurable residual disease status. Application of the algorithm in two independent series of patients with AL predicted for different survival. CONCLUSION: We developed an open-access algorithm for the identification of MGUS-like patients with distinct clinical outcomes. This phenotypic classification could become part of the diagnostic workup of MM and AL amyloidosis.

4th Department of Medicine Haematology Charles University Hospital Hradec Králové Czech Republic

Amyloidosis and Myeloma Unit Department of Hematology Hospital Clínic de Barcelona IDIBAPS Barcelona Spain

Clínica Universidad de Navarra Centro de Investigación Médica Aplicada Universidad de Navarra CCUN IDISNA CIBERONC Pamplona Spain

Department of Haematooncology University Hospital Ostrava Ostrava Czech Republic

Department of Hematology University Hospital Vall d'Hebron Barcelona Spain

Department of Molecular Medicine University of Pavia and Amyloidosis Research and Treatment Center Fondazione IRCCS Policlinico San Matteo Pavia Italy

Hematology Department Hospital Costa del Sol Marbella Marbella Spain

Hematology Department Hospital Universitario 12 de Octubre CIBERONC Instituto de Investigación IMAS12 Madrid Spain

Hematology Department University Hospital La Fe Valencia Spain

Hospital Clínico San Carlos Madrid Spain

Hospital Clínico Universitario Lozano Blesa Zaragoza Spain

Hospital Clínico Universitario Virgen de la Arrixaca IMIB Arrixaca University of Murcia Murcia Spain

Hospital de Cabueñes Gijón Spain

Hospital Morales Meseguer IMIB Arrixaca Universidad de Murcia Murcia Spain

Hospital Universitario de Canarias Santa Cruz de Tenerife Spain

Hospital Universitario de Salamanca CIBERONC Salamanca Spain

Hospital Universitario de Salamanca Department of Medicine and Cytometry Service University of Salamanca CIBERONC Salamanca Spain

Hospital Universitario La Fe Valencia Spain

Hospital Universitario Puerta de Hierro Hospital Madrid Spain

Hospital Universitario Son Espases Palma Spain

Institut Català d'Oncologia and Institut Josep Carreras Hospital Germans Trias i Pujol Barcelona Spain

Myeloma Center Division of Hematology Oncology Winthrop P Rockefeller Cancer Institute University of Arkansas for Medical Sciences Little Rock AR

Tom Baker Cancer Center Department of Hematology University of Calgary Calgary AB Canada

Citace poskytuje Crossref.org

Real-World Evidence on Prognostic Value of MRD in Multiple Myeloma Using Flow Cytometry