The value of minimal residual disease (MRD) in multiple myeloma (MM) has been more frequently investigated in transplant-eligible than elderly patients. Since an optimal balance between treatment efficacy and toxicity is of utmost importance in elderly MM, sensitive MRD monitoring might be particularly valuable in this patient population. Here, we used 2nd generation 8-color multiparameter-flow-cytometry (MFC) to monitor MRD in 162 transplant-ineligible MM patients enrolled in the PETHEMA/GEM2010MAS65 study, The transition from 1st to 2nd generation MFC resulted in increased sensitivity, and allowed to identify three patient groups according to MRD levels: MRD-negative (75-years (HR:4.8; P<.001), and those with high-risk cytogenetics (HR:12.6; P=.01). Using 2nd generation MFC, immune profiling concomitant to MRD monitoring also contributed to identify patients with poor, intermediate and favorable outcome (25%, 61% and 100% OS at 3-years; P=.01); the later patients being characterized by an increased compartment of mature B-cells. Our results show that similarly to transplant-candidates, MRD monitoring is one of the most relevant prognostic factors in elderly MM, irrespectively of patients’ age and cytogenetic risk
