Long-term outcomes by bone marrow B-cell depletion from the R2W trial of bortezomib with cyclophosphamide and rituximab in Waldenstrőm macroglobulinaemia

There remains a lack of consensus as to the most appropriate primary therapy in Waldenstrőm macroglobulinemia (WM). We evaluated a novel bortezomib-based combination and developed a sensitive WM-specific flow cytometry assay (limit of detection 0.004% of leucocytes) to assess bone marrow (BM) response. Sixty treatment-naïve WM patients were enroled into this phase II trial and randomised (2:1) to receive cyclophosphamide and rituximab with either bortezomib (BRC) or fludarabine (FCR). The primary objective was to assess the overall response rate (ORR) in eligible patients receiving BRC (N = 41). An ORR of 97.6% (95%CI:87.1-99.9) was observed; 27 (65.9%) patients remain alive without progression after 62.6 months median follow-up, with 2-, 3- and 5-year progression-free survival (PFS) rates of 92.7% (95%CI:79.0-97.6), 80.5% (95%CI:64.8-89.7) and 65.5% (95%CI:48.8-77.9). Persistent WM B-cells were demonstrable in 19/38 patients at the end of treatment (median 0.24%, range 0.02-11.2%). PFS was markedly longer in patients with BM B-cell depletion (<0.004%) compared to those who had persistent BM B-cells detectable at end of treatment (HR = 0.06, 95%CI:0.01-0.47, p < 0.001), and remained independently associated after adjusting for baseline risk stratification or investigator-assessed response. BRC is a tolerable, highly efficacious regimen for treatment-naïve WM patients. BM B-cell depletion is independently associated with patient outcomes.

Minimal residual disease status improved the response evaluation in patients with Waldenström's macroglobulinemia

Introduction

Minimal residual disease (MRD) has been recognized as an important prognostic factor of survival in patients with hematological malignancies. However, the prognostic value of MRD in Waldenström macroglobulinemia (WM) remains unexplored.

Methods

We analyzed 108 newly diagnosed WM patients receiving systematic therapy and assessed for MRD by multiparameter flow cytometry (MFC) using bone marrow samples.

Results

Of the total patients, 34 (31.5%) achieved undetectable MRD (uMRD). A hemoglobin level of >115 g/L (P=0.03), a serum albumin level of >35 g/L (P=0.01), a β2-MG level of ≤3 mg/L (P=0.03), and a low-risk International Prognostic Scoring System for WM (IPSSWM) stage (P<0.01) were associated with a higher rate of uMRD. Improvements in monoclonal immunoglobulin (P<0.01) and hemoglobin (P=0.03) levels were more evident in uMRD patients compared with that in MRD-positive patients. The 3-year progression-free survival (PFS) was better in uMRD patients compared with that in MRD-positive patients (96.2% vs. 52.8%; P=0.0012). Landmark analysis also showed that uMRD patients had better PFS compared with MRD-positive patients after 6 and 12 months. Patients who achieved partial response (PR) and uMRD had a 3-year PFS of 100%, which was significantly higher than that of patients with MRD-positive PR (62.6%, P=0.029). Multivariate analysis showed that MRD positivity was an independent factor of PFS (HR: 2.55, P=0.03). Moreover, the combination of the 6th International Workshop on WM assessment (IWWM-6 Criteria) and MRD assessment had a higher 3-year AUC compared with the IWWM-6 criteria alone (0.71 vs. 0.67).

Discussion

MRD status assessed by MFC is an independent prognostic factor for PFS in patients with WM, and its determination could improve the precision of response evaluation, especially in patients who achieved PR.

Preneoplastic somatic mutations including MYD88L265P in lymphoplasmacytic lymphoma

Normal cell counterparts of solid and myeloid tumors accumulate mutations years before disease onset; whether this occurs in B lymphocytes before lymphoma remains uncertain. We sequenced multiple stages of the B lineage in elderly individuals and patients with lymphoplasmacytic lymphoma, a singular disease for studying lymphomagenesis because of the high prevalence of mutated MYD88. We observed similar accumulation of random mutations in B lineages from both cohorts and unexpectedly found MYD88^L265P in normal precursor and mature B lymphocytes from patients with lymphoma. We uncovered genetic and transcriptional pathways driving malignant transformation and leveraged these to model lymphoplasmacytic lymphoma in mice, based on mutated MYD88 in B cell precursors and BCL2 overexpression. Thus, MYD88^L265P is a preneoplastic event, which challenges the current understanding of lymphomagenesis and may have implications for early detection of B cell lymphomas.

Time to Move to the Single-Cell Level: Applications of Single-Cell Multi-Omics to Hematological Malignancies and Waldenström's Macroglobulinemia-A Particularly Heterogeneous Lymphoma

Single-cell sequencing techniques have become a powerful tool for characterizing intra-tumor heterogeneity, which has been reflected in the increasing number of studies carried out and reported. We have rigorously reviewed and compiled the information about these techniques inasmuch as they are relative to the area of hematology to provide a practical view of their potential applications. Studies show how single-cell multi-omics can overcome the limitations of bulk sequencing and be applied at all stages of tumor development, giving insights into the origin and pathogenesis of the tumors, the clonal architecture and evolution, or the mechanisms of therapy resistance. Information at the single-cell level may help resolve questions related to intra-tumor heterogeneity that have not been previously explained by other techniques. With that in mind, we review the existing knowledge about a heterogeneous lymphoma called Waldenström's macroglobulinemia and discuss how single-cell studies may help elucidate the underlying causes of this heterogeneity.

Onsets of progression and second treatment determine survival of patients with symptomatic Waldenström macroglobulinemia

Few reports assess prognosis during follow-up of patients with symptomatic Waldenström macroglobulinemia (WM). In 121 WM patients treated between 1993 and 2016, we analyzed the prognostic role during the clinical course of the initial International Prognostic Scoring System for WM (IPSSWM). Then, we assessed onset of response, progression, and second treatment initiation coded as time-dependent covariates. High-risk IPSSWM was an adverse prognostic factor for survival after first treatment initiation (SAFTI). Nevertheless, the corresponding Dxy concordance index obtained in multiple landmark analyses decreased from 0.24 to 0.08 during the first 6 years, in accordance with a departure from the proportional hazard assumption. By contrast with onset of response (whatever its level), onset of progression and initiation of second-line treatment retained prognostic value for SAFTI (P = .02 and P = .006, respectively). These findings were confirmed in cause-specific Cox models for deaths related to WM, but not for unrelated deaths. Time to progression after first-line treatment and time to initiation of second-line treatment had no prognostic value for survival after these 2 events. These results were confirmed in an independent series of 119 patients homogeneously treated with chemoimmunotherapy. Finally, after second-line and third-line treatment, onset of progression had significant prognostic value for subsequent risk of related death only. Thus, taking initial IPSSWM and delayed response to treatment into account, only onset of progression and second treatment initiation provided additional prognostic information for SAFTI. Therefore, progression-free survival or time to next treatment may be satisfactory surrogate end points of SAFTI in WM.

Current applications of multiparameter flow cytometry in plasma cell disorders

Multiparameter flow cytometry (MFC) has become standard in the management of patients with plasma cell (PC) dyscrasias, and could be considered mandatory in specific areas of routine clinical practice. It plays a significant role during the differential diagnostic work-up because of its fast and conclusive readout of PC clonality, and simultaneously provides prognostic information in most monoclonal gammopathies. Recent advances in the treatment and outcomes of multiple myeloma led to the implementation of new response criteria, including minimal residual disease (MRD) status as one of the most relevant clinical endpoints with the potential to act as surrogate for survival. Recent technical progress led to the development of next-generation flow (NGF) cytometry that represents a validated, highly sensitive, cost-effective and widely available technique for standardized MRD evaluation, which also could be used for the detection of circulating tumor cells. Here we review current applications of MFC and NGF in most PC disorders including the less frequent solitary plasmocytoma, light-chain amyloidosis or Waldenström macroglobulinemia.

Response assessment in Waldenström macroglobulinaemia: update from the VIth International Workshop

This report represents a further update of the consensus panel criteria for the assessment of clinical response in patients with Waldenström macroglobulinaemia (WM). These criteria have been updated in light of further data demonstrating an improvement in categorical responses with new drug regimens as well as acknowledgement of the fact that such responses are predictive of overall outcome. A number of key changes are proposed but challenges do however remain and these include the variability in kinetics of immunoglobulin M (IgM) reduction with different treatment modalities and the apparent discrepancy between IgM and bone marrow/tissue response noted with some regimens. Planned sequential bone marrow assessments are encouraged in clinical trials.