Minimal residual disease monitoring and immune profiling in multiple myeloma in elderly patients

Abstract

The value of minimal residual disease (MRD) in multiple myeloma (MM) has been more frequently investigated in transplant-eligible patients than in elderly patients. Because an optimal balance between treatment efficacy and toxicity is of utmost importance in patients with elderly MM, sensitive MRD monitoring might be particularly valuable in this patient population. Here, we used second-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 first- to second-generation MFC resulted in increased sensitivity and allowed us to identify 3 patient groups according to MRD levels: MRD negative (<10; n = 54, 34%), MRD positive (between <10 and ≥10; n = 20, 12%), and MRD positive (≥10; n = 88, 54%). MRD status was an independent prognostic factor for time to progression (TTP) (hazard ratio [HR], 2.7; P = .007) and overall survival (OS) (HR, 3.1; P = .04), with significant benefit for MRD-negative patients (median TTP not reached, 70% OS at 3 years), and similar poorer outcomes for cases with MRD levels between <10 and ≥10 vs ≥10 (both with a median TTP of 15 months; 63% and 55% OS at 3 years, respectively). Furthermore, MRD negativity significantly improved TTP of patients >75 years (HR, 4.8; P < .001), as well as those with high-risk cytogenetics (HR, 12.6; P = .01). Using second-generation MFC, immune profiling concomitant to MRD monitoring also contributed to identify patients with poor, intermediate, and favorable outcomes (25%, 61%, and 100% OS at 3 years, respectively; 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 patients, irrespectively of age or cytogenetic risk.