Although multiparameter flow cytometry (MFC) has demonstrated clinical relevance in monoclonal gammopathy of undetermined significance (MGUS)/myeloma, immunophenotypic studies on the full spectrum of Waldenström's Macroglobulinemia (WM) remain scanty. Herein, a comprehensive MFC analysis on bone marrow samples from 244 newly diagnosed patients with an immunoglobulin M (IgM) monoclonal protein was performed, including 67 IgM-MGUS, 77 smoldering and 100 symptomatic WM. Our results show a progressive increase on the number and light-chain-isotype-positive B-cells from IgM-MGUS to smoldering and symptomatic WM (P<.001), with only 1% of IgM-MGUS patients showing >10% B cells or 100% light-chain-isotype-positive B-cells (P<.001). Complete light-chain restriction of the B-cell compartment was an independent prognostic factor for time-to progression in smoldering WM (median 26 months; HR: 19.8, P=0.001) and overall survival in symptomatic WM (median 44 months; HR: 2.6, P=0.004). The progressive accumulation of light-chain-isotype-positive B-cells accompanied the emergence of a characteristic Waldenstrom's phenotype (CD22(+dim) / CD25+ /CD27+ / IgM+) that differed from other B-NHL by negative expression of CD5, CD10, CD11c or CD103. In contrast to myeloma, light-chain-isotype-positive plasma cells in IgM monoclonal gammopathies show otherwise normal antigenic expression. Our results highlight the potential value of MFC immunophenotyping for the characterization of the Waldenström's clone, as well as for the differential diagnosis, risk of progression and survival in WM.

Key Points• Benign (ie, IgM MGUS and smoldering WM) clonal B cells already harbor the phenotypic and molecular signatures of the malignant WM clone.• Multistep transformation from benign (ie, IgM MGUS and smoldering WM) to malignant WM may require specific copy number abnormalities.Although information about the molecular pathogenesis of Waldenström macroglobulinemia (WM) has significantly advanced, the precise cell of origin and the mechanisms behind WM transformation from immunoglobulin-M (IgM) monoclonal gammopathy of undetermined significance (MGUS) remain undetermined. Here, we undertook an integrative phenotypic, molecular, and genomic approach to study clonal B cells from newly diagnosed patients with IgM MGUS (n 5 22), smoldering (n 5 16), and symptomatic WM (n 5 11). Through principal component analysis of multidimensional flow cytometry data, we demonstrated highly overlapping phenotypic profiles for clonal B cells from IgM MGUS, smoldering, and symptomatic WM patients. Similarly, virtually no genes were significantly deregulated between fluorescence-activated cell sorter-sorted clonal B cells from the 3 disease groups. Interestingly, the transcriptome of the Waldenström B-cell clone was highly different than that of normal CD25 2 CD22 1 B cells, whereas significantly less genes were differentially expressed and specific WM pathways normalized once the transcriptome of the Waldenström B-cell clone was compared with its normal phenotypic (CD25 1 CD221low ) B-cell counterpart. The frequency of specific copy number abnormalities [14, del(6q23.3-6q25.3), 112, and 118q11-18q23] progressively increased from IgM MGUS and smoldering WM vs symptomatic WM (18% vs 20% and 73%, respectively; P 5 .008), suggesting a multistep transformation of clonal B cells that, albeit benign (ie, IgM MGUS and smoldering WM), already harbor the phenotypic and molecular signatures of the malignant Waldenström clone. (Blood. 2015;125(15):2370-2380

Key Points MFC is a valuable biomarker to discriminate “true” SBP patients from those with “occult” BM clonal PCs and high-risk of progression to MM.

Background and Aims There is little information on the incremental prognostic importance of frailty beyond conventional prognostic variables in heart failure (HF) populations from different country income levels. Methods A total of 3429 adults with HF (age 61 ± 14 years, 33% women) from 27 high-, middle- and low-income countries were prospectively studied. Baseline frailty was evaluated by the Fried index, incorporating handgrip strength, gait speed, physical activity, unintended weight loss, and self-reported exhaustion. Mean left ventricular ejection fraction was 39 ± 14% and 26% had New York Heart Association Class III/IV symptoms. Participants were followed for a median (25th to 75th percentile) of 3.1 (2.0–4.3) years. Cox proportional hazard models for death and HF hospitalization adjusted for country income level; age; sex; education; HF aetiology; left ventricular ejection fraction; diabetes; tobacco and alcohol use; New York Heart Association functional class; HF medication use; blood pressure; and haemoglobin, sodium, and creatinine concentrations were performed. The incremental discriminatory value of frailty over and above the MAGGIC risk score was evaluated by the area under the receiver-operating characteristic curve. Results At baseline, 18% of participants were robust, 61% pre-frail, and 21% frail. During follow-up, 565 (16%) participants died and 471 (14%) were hospitalized for HF. Respective adjusted hazard ratios (95% confidence interval) for death among the pre-frail and frail were 1.59 (1.12–2.26) and 2.92 (1.99–4.27). Respective adjusted hazard ratios (95% confidence interval) for HF hospitalization were 1.32 (0.93–1.87) and 1.97 (1.33–2.91). Findings were consistent among different country income levels and by most subgroups. Adding frailty to the MAGGIC risk score improved the discrimination of future death and HF hospitalization. Conclusions Frailty confers substantial incremental prognostic information to prognostic variables for predicting death and HF hospitalization. The relationship between frailty and these outcomes is consistent across countries at all income levels.

936 Demonstration of bone marrow (BM) infiltration by lymphoplasmacytic lymphoma is essential to the diagnosis of WM, and a trephine biopsy is considered mandatory for this assessment. Multiparameter flow cytometry (MFC) has demonstrated its clinical relevance in MGUS and myeloma; however, immunophenotypic studies on IgM monoclonal gammopathies are scanty, and focus only in patients with WM. Herein, MFC immunophenotyping was performed on BM samples from 244 patients, including 67 IgM MGUS, 77 smoldering, and 100 symptomatic WM newly diagnosed patients according to the Second International Workshop. A four color panel that systematically allowed the identification of B cells and plasma cells (PC), and their phenotypic characterization for a total of 24 antigens was used. We first analyzed the percentage of B cells and PC in BM and the percentage of light chain restricted cells in both compartments. Our results show a progressive increment of B cells from IgM MGUS to smoldering and symptomatic WM (medians of 2%, 9% and 12%; P<.001), as well of light chain restricted B cells (75%, 96% and 99%; P<.001). In contrast, no differences were found for the percentage of PC (median of 0.3%), but light chain restricted PC progressively increased from IgM MGUS to smoldering and symptomatic WM (70%, 85% and 97%; P<.001). Accordingly, only 1% of IgM MGUS patients showed >10% B cells, in contrast to 34% and 55% of smoldering and symptomatic WM (P<.001). Likewise, only 1% of IgM MGUS patients showed 100% light chain restricted B cells, in contrast to 19% and 40% of smoldering and symptomatic WM (P<.001); similar results being also found using a cutoff of 100% light chain restricted PC. Subsequently, we explored whether the percentages of BM and light chain restricted B cells and PC could predict time to progression (TTP) from smoldering into symptomatic WM, as well as overall survival (OS) in symptomatic WM. In smoldering WM, B cells (>10% vs ≤10%: median TTP of 47m vs 145m; P=.016) and light chain restricted B cells (100% vs <100%: 26m vs 145m; P<.001) but not PC, predicted risk of progression. On the multivariate analysis that included serum M-spike (±3g/dL), BM infiltration (±50% lymphoplasmacytic cells), BM B-cells and light chain restricted B cells (by MFC), only the later retained independent prognostic value (HR: 19.8, P=.001). Upon analyzing factors influencing survival in symptomatic WM patients, cases with >10% B cells showed a trend for inferior OS (P=.080), and significant differences emerged when comparing patients with 100% vs <100% light chain restricted B cells (median OS 44m vs 78m; P=.001). The later marker was independent (HR: 2.6; P=.004) of the International Prognostic Scoring System (HR: 2.2; P=.006). Focusing on the antigenic profiles of B cells and PC, we noted that within the B-cell compartment there was a progressive increment of CD22dim (69%, 92% and 88%; P<.001), CD25+ (61%, 88% and 90%; P<.001) and sIgM+ (88%, 95% and 97%; P=.002) B cells from IgM MGUS to smoldering and symptomatic WM. This underlies that the accumulating light chain restricted clonal B cells show a characteristic Waldenstrom's phenotype (CD22dim/CD25+/IgM+). Of note, a bimodal (from - to +) expression for the B cell memory marker CD27 was found in >50% of WM patients, which raises the possibility that the WM clone may arise, at least in some cases, before antigenic stimulation; subsequent maturation of the clone into PC would explain the typical presence of somatic hypermutations. On the other hand, B-cells from IgM MGUS and WM patients were negative in ≥90% of cases for CD5, CD10, CD11c and CD103, which can be useful to differentiate between WM and other B-NHL. Finally, the antigenic profile of PC in IgM MGUS and WM was similar to that of normal PC, and different from myeloma PC by consistently showing a CD27+ and CD56- phenotype, in addition to sIgM+ expression in ≥87% of all cases. Similarly to B-cells, we also noted that within the PC compartment there was a progressive increment of CD19+, CD45+ and sIgM+ CD20+ PC from IgM MGUS to smoldering and symptomatic WM. This underlies that this transition is asssociated with an accumulation of light chain restricted clonal PC displaying an immature/plasmablastic phenotype. In summary, our results highlight the potential value of MFC immunophenotyping for the characterization of the Waldenström's clone, as well as for the differential diagnosis, risk of progression and survival in WM. Disclosures: No relevant conflicts of interest to declare.