Risk of progression in smouldering myeloma and monoclonal gammopathies of unknown significance: comparative analysis of the evolution of monoclonal component and multiparameter flow cytometry of bone marrow plasma cells.

The present study explored the impact of two novel criteria; having >95% abnormal plasma cells by flow cytometry at diagnosis and the evolving subtype of the disease, as predictors of progression in 61 smouldering multiple myeloma (SMM) and 311 monoclonal gammopathy of unknown significance (MGUS) patients. Although both criteria were of prognostic value, the risk of progression was better identified by immunophenotyping [Hazard Ratio (HR) 6.2 and 17.2 for SMM and MGUS, respectively] than evolving subtype, which had independent prognostic value only in MGUS (HR 3.6). Immunophenotyping discriminated the different risk of progression within the evolving and non-evolving subgroups of SMM (P = 0.01) and MGUS (P < 0.001).

New criteria to identify risk of progression in monoclonal gammopathy of uncertain significance and smoldering multiple myeloma based on multiparameter flow cytometry analysis of bone marrow plasma cells.

Monoclonal gammopathy of uncertain significance (MGUS) and smoldering multiple myeloma (SMM) are plasma cell disorders with a risk of progression of approximately 1% and 10% per year, respectively. We have previously shown that the proportion of bone marrow (BM) aberrant plasma cells (aPCs) within the BMPC compartment (aPC/BMPC) as assessed by flow cytometry (FC) contributes to differential diagnosis between MGUS and multiple myloma (MM). The goal of the present study was to investigate this parameter as a marker for risk of progression in MGUS (n = 407) and SMM (n = 93). Patients with a marked predominance of aPCs/BMPC (> or = 95%) at diagnosis displayed a significantly higher risk of progression both in MGUS and SMM (P< .001). Multivariate analysis for progression-free survival (PFS) selected the percentage aPC/BMPC (> or = 95%) as the most important independent variable, together with DNA aneuploidy and immunoparesis, for MGUS and SMM, respectively. Using these independent variables, we have identified 3 risk categories in MGUS (PFS at 5 years of 2%, 10%, and 46%, respectively; P< .001) and SMM patients (PFS at 5 years of 4%, 46%, and 72%, respectively; P < .001). Our results show that multiparameter FC evaluation of BMPC at diagnosis is a valuable tool that could help to individualize the follow-up strategy for MGUS and SMM patients.

Immunophenotypic analysis of peripheral blood stem cell harvests from patients with multiple myeloma.

BACKGROUND AND OBJECTIVES: Four-color multiparameter immunophenotyping has recently proven to be an attractive technique for evaluating the plasma cell (PC) compartment since it allows discrimination between myelomatous and normal PC. This study was designed to investigate: i) whether peripheral blood is less contaminated than bone marrow as a source for an autologous transplant; ii) the effect of growth factors on mobilizing myelomatous PC into peripheral blood; iii) the degree of contamination by myelomatous PC in apheresis samples; and iv) whether the number of PC increases during the last days of apheresis. DESIGN AND METHODS: Using 4-color antigen staining we investigated the composition of the PC compartment in 90 apheresis products from 40 patients with MM; in 17 cases bone marrow and peripheral blood samples were also simultaneously evaluated. RESULTS: (i) All pre-mobilization bone marrow samples analyzed were always contaminated with myelomatous PC whereas only 41% of the post-mobilization peripheral blood samples were contaminated. Moreover, the use of peripheral blood would lead to a reduction of >5x10(5) infused myelomatous PC; (ii) mobilization with cytokines increased the number of circulating PC, generally because of an expansion of the normal PC population; (iii) forty-eight percent of all peripheral blood stem cell harvests were contaminated with myelomatous PC, although normal PC usually represented the predominant population; (iv) no significant changes were observed in the amount of contaminating myelomatous PC during the first three days of apheresis. INTERPRETATION AND CONCLUSIONS: Multiparameter immunophenotyping is a useful approach for investigating the PC compartment in apheresis products.

Immunophenotypic evaluation of the plasma cell compartment in multiple myeloma: a tool for comparing the efficacy of different treatment strategies and predicting outcome.

Multiparametric immunophenotyping can be a sensitive method for analyzing the plasma cell (PC) compartment in patients with multiple myeloma because it discriminates between myelomatous and normal PCs. Using this approach, we compared the efficacy of high-dose chemotherapy followed by autologous stem cell transplantation (ASCT) with that of conventional chemotherapy. We found that ASCT provided a significantly greater reduction in the level of residual tumor PCs and with better recovery of normal PCs. This profile of coexistence of normal PCs and myelomatous PCs resembled that observed in monoclonal gammopathy of undetermined significance. We also found that treatment-induced changes in the PC compartment correlated with disease outcome. Thus, patients in whom at least 30% of gated PCs had a normal phenotype after treatment had a significantly longer progression-free survival (60 +/- 6 months versus 34 +/- 12 months; P =.02).