Smoldering multiple myeloma: evolving diagnostic criteria and treatment strategies

The adage for smoldering myeloma (SMM) has been to observe without treatment, until criteria for active multiple myeloma were satisfied. Definitions and risk stratification models have become more sophisticated, with prognostication tailored to include high-risk cytogenetics as per the most recent International Myeloma Working Group 2020 risk model. Moreover, progress in defining genomic evolution and changes in the bone marrow microenvironment through the monoclonal continuum have given insight into the complexities underlying the different patterns of progression observed in SMM. Given recent data showing improved progression-free survival with early intervention in high-risk SMM, the current dilemma is focused on how these patients should be treated. This case-based article maps the significant advancements made in the diagnosis and risk stratification of SMM. Data from landmark clinical trials will also be discussed, and ongoing trials are summarized. Ultimately, we outline our approach to SMM and hope to impart to the reader a sound concept of the current clinical management of SMM.

Advances in MGUS diagnosis, risk stratification, and management: introducing myeloma-defining genomic events

In the 1960s, Dr Jan Waldenström argued that patients who had monoclonal proteins without any symptoms or evidence of end-organ damage represented a benign monoclonal gammopathy. In 1978, Dr Robert Kyle introduced the concept of “monoclonal gammopathy of undetermined significance” (MGUS) given that, at diagnosis, it was not possible with available methods (ie, serum protein electrophoresis to define the concentration of M-proteins and microscopy to determine the plasma cell percentage in bone marrow aspirates) to determine which patients would ultimately progress to multiple myeloma. The application of low-input whole-genome sequencing (WGS) technology has circumvented previous problems related to volume of clonal plasma cells and contamination by normal plasma cells and allowed for the interrogation of the WGS landscape of MGUS. As discussed in this chapter, the distribution of genetic events reveals striking differences and the existence of 2 biologically and clinically distinct entities of asymptomatic monoclonal gammopathies. Thus, we already have genomic tools to identify “myeloma-defining genomic events,” and consequently, it is reasonable to consider updating our preferred terminologies. When the clinical field is ready to move forward, we should be able to consolidate current terminologies—from current 7 clinical categories: low-risk MGUS, intermediate-risk MGUS, high-risk MGUS, low-risk smoldering myeloma, intermediate-risk smoldering myeloma, high-risk smoldering myeloma, and multiple myeloma—to future 3 genomic-based categories: monoclonal gammopathy, early detection of multiple myeloma (in which myeloma-defining genomic events already have been acquired), and multiple myeloma (patients who are already progressing and clinically defined cases). Ongoing investigations will continue to advance the field.

Changing Patterns of Symptomatic Myeloma after the Implementation of the 2014 IMWG Diagnostic Criteria and Reduced Early Mortality

In 2014, the IMWG updated the diagnostic criteria for symptomatic myeloma and in addition to classical "CRAB", implemented "biomarkers of malignancy" (BoM) (FLC ratio>100, more than 1 focal lesion in MRI and bone marrow infiltration of at least 60%). As a result, a subset of patients previously considered as having "smoldering myeloma" were characterized as symptomatic and were eligible to start therapy; these criteria are also adopted in clinical trials. However, the impact of the 2014 IMWG criteria in the overall clinical presentation of symptomatic myeloma patients who start therapy or in the outcomes of patients who present only with biomarkers of malignancy, has not been fully appreciated. We evaluated the characteristics and outcomes of patients who started therapy in the past 5 years, when the 2014 IMWG criteria were implement in our clinical practice and compare their characteristics and outcomes with those of patients that started in an earlier period. To adjust for advances in diagnosis and especially imaging, the analysis included 1007 consecutive patients who started therapy in the Department of Clinical Therapeutics between 1/1/2010 and 31/12/2020. Our prospectively maintained database includes all consecutive patients who start therapy for myeloma. The patients were divided in two cohorts: those that started therapy after 1/1/2015 (after 2014 IMWG criteria implementation) and those that started therapy between 1/1/2010 and 31/12/2014. In these two chronological periods, methods for the assessment of disease were similar except for wider use of ldWBCT after 2013 and more frequent use of conventional CT before 2013. In the 2010-2014 period, 393 patients started therapy vs 614 that started between 2015-2020. Patients in the two groups had similar age (mean 67 vs 66.3, p=0.399) and similar b2-microglobulin levels (7.39 vs 7.33 mg/L, p=0.907) but hemoglobin (mean 10.2 vs 10.6 gr/dl, p=0.016), platelet counts (mean 230 vs 246 x10 9/L, p=0.021), serum albumin (3.6 vs 3.8 gr/dl, p=0.003) were higher in the 2015-2020 era. Although it did not reach statistical significance, mean bone marrow infiltration in trephine biopsy (60.5% vs 57.3%, p=0.056) and eGFR (mean 66.6 vs 62.3 ml/min/ 1.73 m2, p=0.057) were higher and mean serum calcium levels lower (9.9 vs 10.2 mg/dl, p=0.073) in 2015-2020 group, while, serum LDH >ULN (19.6% vs 21.4%, p=0.513) and high risk cytogenetics (20.4% vs 20.8%) were found in similar rates. Accordingly, ISS and R-ISS stage distribution was similar (p=0.496). Per CRAB criteria, hemoglobin < 10 gr/dl was present in 48.9% of patients in the 2010-14 period vs 43.6% in the 2015-2020 (p=0.1), hypercalcemia in 18.2% vs 15% (p=0.185), serum creatinine ≥2 mg/dl in 22% vs 18% (p=0.124) and lytic bone disease in 76.9% vs 76.8%, p=0.973). At least one CRAB was present in 96.4% vs 94% of patients in the two periods (p=0.603). Even in the era before the publication of the 2014 IMWG criteria, 3.6% of patients that started therapy did not fulfill the CRAB criteria of that time; in retrospect, most had at least one BoM present. In the 2015-2020 period, 6% of new patients were considered as symptomatic based on the presence of BoM only. The median follow-up of the 2010-2014 cohort is 63 months and is 25 months for the 2015-2020 group; the 1- and 2-year OS is 83% vs 90% and 75% vs 79% respectively (p=0.057) for the two groups; early mortality (within 3 months from start of therapy) was 7.4% vs 3.9% (p=0.016) respectively. The OS of patients starting therapy based on the presence of BoM only is not reached (3-year OS 87%) vs 59 months (3 year OS: 65%) for patients presenting with CRAB (p=0.051). Because there may be a lead time bias, we also compare the OS of patients with biomarkers of malignancy only vs those with CRAB and ISS-1 disease: OS was similar although with a trend towards better OS for those with BoM. In conclusion, the implementation of the 2014 IMWG diagnostic criteria has resulted in about 6% of newly diagnosed patients starting therapy based only on the presence of BoM. Although the implementation of the criteria has resulted in slightly better clinical presentation (less severe CRAB) and reduced early mortality, most patients still present with disease complications. These data point to the need to develop tools that can identify myeloma patients earlier during their disease course, before they develop devastating complications, in order to further improve their outcomes and quality of life. Disclosures Kastritis: Janssen: Consultancy, Honoraria, Research Funding; Pfizer: Consultancy, Honoraria, Research Funding; Takeda: Honoraria; Genesis Pharma: Honoraria; Amgen: Consultancy, Honoraria, Research Funding. Gavriatopoulou: Karyopharm: Honoraria; Takeda: Honoraria; Janssen: Honoraria; Sanofi: Honoraria; Genesis: Honoraria; GSK: Honoraria; Amgen: Honoraria. Terpos: Novartis: Honoraria; Janssen: Consultancy, Honoraria, Research Funding; Genesis: Consultancy, Honoraria, Research Funding; Celgene: Consultancy, Honoraria, Research Funding; BMS: Honoraria; Amgen: Consultancy, Honoraria, Research Funding; Takeda: Consultancy, Honoraria, Research Funding; Sanofi: Consultancy, Honoraria, Research Funding; GSK: Honoraria, Research Funding. Dimopoulos: Takeda: Honoraria; BMS: Honoraria; Amgen: Honoraria; Beigene: Honoraria; Janssen: Honoraria.

Lenalidomide and Pomalidomide Improve Function and Induce FcγRI/CD64 in Multiple Myeloma Neutrophils

Background Myeloid dysfunction is an emerging hallmark of microenvironment changes occurring in multiple myeloma (MM). Our previous work showed that FcγRI/CD64 overexpression in neutrophils of newly diagnosed MM patients is associated to inferior outcomes, reduced oxidative bursts and phagocytosis, with an increased risk of bacterial infections. Pomalidomide is a novel immune-modulatory drug approved for relapsed/refractory patients (RRMM), with drug-related neutropenia as major limitation to treatment. Patients and methods Herein, we describe a prospective analysis of 51 consecutive RRMM patients treated with pomalidomide and dexamethasone (PomDex) from March 2015 through December 2016, associated with secondary prophylaxis with filgrastim (G-CSF) in case of neutrophil count <1500 cells/μL. Neutrophil function was investigated by flow cytometry, including the phagocytosis, oxidative bursts, and median fluorescence intensity of FcγRI-CD64. Controls included a group of newly diagnosed symptomatic MM (NDMM), asymptomatic (smoldering myeloma, MGUS) and healthy subjects referred to our Center in the same time-frame. Results Compared to controls, RRMM neutrophils had higher expression of FcγRI/CD64 and lower phagocytic activity and oxidative bursts. We maintained median leukocyte counts higher than 3.5· 10^9/L for 6 cycles, and median neutrophil counts higher than 1.5 · 10^9/L, with only 6 (11%) patients developing grade 3–4 infections, without pomalidomide dose reduction. After 4 cycles of PomDex, FcγRI/CD64 was further increased in neutrophils, and phagocytic activity and oxidative bursts recovered independently from filgrastim exposure and the quality of hematological responses. Similarly, in NDMM patients, lenalidomide but not bortezomib upregulated FcγRI/CD64 expression, improving phagocytic activity and oxidative bursta as tested in vitro. Conclusions Our combined biological and clinical data provide new information on the ability of pomalidomide and lenalidomide to modulate the functional activity of neutrophils, despite their chronic activation due to FcγRI/CD64 overexpression.

Clonal Evolution of Multiple Myeloma—Clinical and Diagnostic Implications

Plasma cell dyscrasias are a heterogeneous group of diseases characterized by the expansion of bone marrow plasma cells. Malignant transformation of plasma cells depends on the continuity of events resulting in a sequence of well-defined disease stages, from monoclonal gammopathy of undetermined significance (MGUS) through smoldering myeloma (SMM) to symptomatic multiple myeloma (MM). Evolution of a pre-malignant cell into a malignant cell, as well as further tumor progression, dissemination, and relapse, require development of multiple driver lesions conferring selective advantage of the dominant clone and allowing subsequent evolution under selective pressure of microenvironment and treatment. This process of natural selection facilitates tumor plasticity leading to the formation of genetically complex and heterogenous tumors that are notoriously difficult to treat. Better understanding of the mechanisms underlying tumor evolution in MM and identification of lesions driving the evolution from the premalignant clone is therefore a key to development of effective treatment and long-term disease control. Here, we review recent advances in clonal evolution patterns and genomic landscape dynamics of MM, focusing on their clinical implications.