Quantitative immunoprecipitation mass spectrometry (QIP-MS) allows the identification of the M-protein in patients with multiple myeloma (MM) otherwise in complete response, and could be considered suitable for measurable residual disease (MRD) evaluation in peripheral blood. In the context of the GEM2012MENOS65 and GEM2014MAIN trials, we compared the performance of QIP-MS in serum with next-generation flow (NGF) cytometry in bone marrow to assess MRD in paired samples obtained postinduction, transplant, consolidation and after 24 cycles of maintenance. At each time point, both NGF and QIP-MS were able to segregate 2 groups of patients with significantly different progression-free survival; when the evolution of the results obtained with either method was considered, maintaining or converting to MRD negativity was associated with longer survival, significantly better when compared with sustaining or converting to MRD positivity. Reemergence of MRD by QIP-MS was associated with high risk of imminent clinical progression. In conclusion, MRD evaluation by NGF and MS achieves similar prognostic value based in single time point assessments and kinetics. Thus, the minimally invasive nature of MRD monitoring by MS represents a breakthrough in highly sensitive response assessment in MM. The trials were registered at www.clinicaltrials.gov as #NCT01916252 (GEM2012MENOS65) and at EudraCT as #2012-005683-10; and as #NCT02406144 (GEM2014MAIN) and at EudraCT as 2014-00055410.
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