An update on biology, diagnosis and treatment of primary plasma cell leukemia

European Myeloma Network Group review and consensus statement on primary plasma cell leukemia

BACKGROUND

Primary plasma cell leukemia (PPCL) is the most aggressive disorder among plasma cell malignancies, with new diagnostic criteria recently established by the International Myeloma Working Group. Studies have shown that PPCL patients receiving a combination of novel agents, but not eligible for transplantation, may have a median survival up to 2 years, extended to 3 years or more in those undergoing transplant procedures. These findings remain unsatisfactory, particularly if compared with progresses obtained in multiple myeloma.

DESIGN

A European Myeloma Network (EMN) expert panel reviewed the most recent literature and selected the areas of major concern in the management of PPCL by generating and rank ordering key questions using the criterion of clinical relevance. Multistep procedures were utilized to achieve a consensus on recommendations. The Delphi questionnaire method was used and a consensus of at least 80% was reached for all final statements.

RESULTS

An extended overview of current biological, clinical, prognostic, and therapeutic aspects of PPCL, including ongoing and close to start clinical trials, is presented. Furthermore, updated guidelines for the management of PPCL and practical recommendations are provided, in the context of current knowledge about this disease, also looking at possible future perspectives to ameliorate the outcome of these patients.

CONCLUSIONS

PPCL still remains an unmet clinical need. Notwithstanding, some not negligible progresses have been recently achieved. The European Myeloma Network panel strongly support ongoing and planned clinical trials, as well as biological studies based on novel technologies, strategies, and treatment options that could represent breakthroughs we have been waiting for too long.

Case study: Acute plasmoblastic leukemia presentation following effective haploidentical hematopoietic stem cell transplantation therapy

Plasma cell leukemia is a rare and aggressive malignancy characterized by monoclonal gammopathy and the presence of circulating plasma cells in the peripheral blood. Therapeutic strategies for plasma cell leukemia remain undefined, with treatments primarily borrowed from those used in multiple myeloma. The first-line treatment typically involves a combination of a proteasome inhibitor, an immunomodulatory agent, steroids, and/or anthracyclines and alkylators within an intensive chemotherapy regimen. Following this, consolidation with autologous hematopoietic stem cell transplantation is offered to eligible patients, followed by maintenance therapy. For patients ineligible for autologous hematopoietic stem cell transplantation, allogeneic hematopoietic stem cell transplantation is considered a viable alternative. Given the challenges in securing a fully human leukocyte antigen-matched donor, haploidentical hematopoietic stem cell transplantation serves as a potential salvage therapy, as demonstrated in the clinical case presented. This article presents the case of a female patient in her 50s diagnosed with plasma cell leukemia who, following unsuccessful autologous hematopoietic stem cell mobilization, underwent haploidentical hematopoietic stem cell transplantation from her son, resulting in complete donor chimerism and a favorable response.

Outcomes of hematopoietic stem cell transplantation in primary plasma cell leukemia: A systematic review and meta-analysis

BACKGROUND

Hematopoietic stem cell transplantation (HCT) is a pivotal treatment modality for primary plasma cell leukemia (pPCL). We aimed to examine the outcomes of allogeneic (allo) and autologous (auto) HCT in adult pPCL patients.

METHODS

Following PRISMA guidelines, a comprehensive literature search was performed on PubMed, Cochrane, Embase, and Clinicaltrials.gov using relevant MeSH terms and keywords. Twelve original articles reporting outcomes of auto-HCT or allo-HCT in adult pPCL patients were included. The pooled analysis was performed using the 'meta' package in the R program (version 4.3.0).

RESULTS

Our analysis included 1757 pPCL patients (1535 with auto-HCT, 222 with allo-HCT), and 49 % were males. The pooled 3 years overall survival (OS), progression-free survival/event-free survival (PFS/EFS), and relapse rate (RR) in auto-HCT were 51 % (95 % CI 0.4-0.61, I2=92 %, p = <0.01), 36 % (95 % CI 0.24-0.52, I 2 =97 %, p < 0.01), and 68 % (95 % CI, 0.65-0.71, I2=0 %, p = 0.42), respectively. Among allo-HCT recipients, the reported OS varied from 71 % at 2.3 years to 31 % at 4 years and EFS/PFS from 29 % at 2.5 years to 19 % at 4 years. The pooled treatment-related mortality (TRM) was 12 % (95 % CI 0.05-0.25, I 2=35 %, p = 0.22) at a median of 6 months. The pooled incidence of acute and chronic graft versus host disease was 27 % (0.19-0.36, I2= 30 %, p = 0.21) and 36 % (0.27-0.45, I2= 24 %, p = 0.26), respectively.

CONCLUSION

HCT remains pivotal in treating primary plasma cell leukemia. However, higher relapse rates warrant novel agents and clinical trials to improve transplant-related outcomes in this challenging subgroup.

Atypical Plasma Cell Leukemia Mistaken for Acute Leukemia: A Case Report

The patient we present here had many clinical, morphological, and laboratory findings characteristic of acute leukemia. During the course of the disease, the diagnosis changed from acute leukemia to chronic small B-cell lymphoproliferative disease, a blastoid variant of mantle cell lymphoma, and finally to atypical plasma cell leukemia. Atypical plasma cell leukemia is a rare condition with aggressive biological behavior. Our patient relapsed a short time after achieving complete remission, in spite of aggressive therapy and autologous stem cell transplantation. During relapse, it was possible to morphologically identify malignant cells as being of plasma cell origin, although immature and atypical. Atypical plasma cell leukemia presents a diagnostic challenge as it may mimic other neoplasms both morphologically and clinically. It is also recognized that plasma cell neoplasm immunophenotype may not be entirely specific for its lineage where common diagnostic biomarkers are applied by immunohistochemistry or flow cytometry. Where this is the case, only focused investigation for plasma cell lineage will be more informative. This patient has unusual clinical presentation, a nondescript morphology of the circulating plasma cells, as well as an immunophenotype, detected by the initial panels used for flow cytometry and immunohistochemistry, that was not entirely specific for plasma cells. Such cases present a good reminder of the diagnostic complexity of atypical plasma cell leukemia and emphasize that plasma cell differentiation needs to be interrogated in cases where the initial work-up shows unusual results.

Validation of the revised diagnostic criteria for primary plasma cell leukemia by the Korean Multiple Myeloma Working Party

The International Myeloma Working Group has recently revised the diagnostic criteria for primary plasma cell leukemia (PCL) to circulating plasma cells (CPCs) ≥ 5% in a peripheral blood smear. The present study validated new criteria in patients with multiple myeloma or PCL diagnosed using the previous diagnostic criteria, who were administered immunomodulatory drugs or proteasome inhibitors as induction therapy. We analyzed the medical records of 1357 patients from eight hospitals in South Korea. The median age of the all patients was 64 years, and 187 (13.8%) had CPCs at diagnosis. Only 79 (5.8%) of the patients had ≥ 5% CPCs. The median overall survival (OS) of patients with CPCs ≥ 5% and ≥ 20% was similar, but had significantly inferior median progression-free survival (PFS) and median OS than those with CPCs < 5% (13.1 vs. 21.5 months, P < 0.001, and 21.5 vs. 60.9 months, P < 0.001, respectively). Primary PCL diagnosed using the revised criteria presented with higher total calcium levels and serum creatinine levels, lower platelet counts and frequent organomegaly and plasmacytoma at diagnosis. Univariate and multivariate analyses demonstrated that the presence of plasmacytoma and elevated serum β2-microglobulin were significantly associated with OS in primary PCL. In conclusion, the revised criterion of CPCs ≥ 5% in a peripheral blood smear is appropriate for PCL diagnosis.

Causes of death in primary plasma cell leukemia differ from multiple myeloma: A STROBE-compliant descriptive study based on SEER database

The primary plasma cell leukemia (pPCL) is a rare but aggressive variant of multiple myeloma (MM). Few studies have focused on the differences in the causes of death between pPCL and MM. This study aimed to compare and evaluate the causes of death of patients with pPCL and MM. The data were collected from the Surveillance Epidemiology, and End Results (SEER) database. The demographic characteristics, survival, and causes of death in pPCL and MM patients were evaluated and compared. The competing risk regression model was performed to predict the cause of death. Between 1975 and 2009, the overall mortality rate was 96.13% and 88.71% for pPCL and MM, and the median survival was 9 and 26 months, respectively. In pPCL, leukemia caused 45.05% of the deaths, followed by myeloma (38.83%). In MM, myeloma was the leading cause of death, accounting for 74.89% of the deaths. Older age at diagnosis was a risk factor for dying of leukemia in pPCL patients (HR = 1.49, 95% CI: 1.16-1.91), while older age at death was associated with reduced risk (HR = 0.67, 95% CI: 0.52-0.86). Although the survival of pPCL patients increased with time periods of diagnosis since 1975 to 2009, the risk of dying of leukemia increased with the periods. For MM, most of the demographic characteristics were found to have independently predicting influence on the cause of death. Patients with pPCL and MM had distinct causes of death. Leukemia was the leading and the most serious cause of death in pPCL patients. The demographic factors could not predict the causes of death in pPCL. More large-scale and multi-center studies are needed to evaluate the effect of novel agents in pPCL patients, especially for patients who have progressed to leukemia.

Update on primary plasma cell leukemia

Plasma cell leukemia (PCL) is a rare and highly aggressive plasma cell neoplasm developing in 0.5?4% of patients with multiple myeloma (MM). The diagnostic criteria were recently revised from 20% to ≥5% of circulating plasma cells in peripheral blood smears. PCL is classified as primary or secondary; primary PCL is when it presents in patients with no MM. Primary PCL shows clinical and laboratory features at presentation that differ from MM and exhibits a dismal prognosis even with the use of effective agents against MM. Therefore, intensive chemotherapy should be initiated immediately after diagnosis, and autologous stem cell transplantation is recommended for transplant-eligible patients. Maintenance therapy after transplantation may reduce the rate of early relapses. We reviewed the definitions of PCL, revised diagnostic criteria, clinical features, and appropriate initial treatments for primary PCL.

Transcriptomic Analysis in Multiple Myeloma and Primary Plasma Cell Leukemia with t(11;14) Reveals Different Expression Patterns with Biological Implications in Venetoclax Sensitivity

Simple Summary

The growing interest in BCL2 inhibitors for the treatment of multiple myeloma (MM) has led to the need for biomarkers that are able to predict patient’s sensitivity to the drug. The presence of the chromosomal translocation t(11;14) in MM is mainly associated with sensitivity to venetoclax and good prognosis. The incidence of t(11;14) largely increases in primary Plasma Cell Leukemia (pPCL) in association with an unfavorable outcome. Currently, data concerning pPCL sensitivity to venetoclax are virtually absent. In this context, we investigated the transcriptome of MM and pPCL with t(11;14), evidencing that the two clinical entities are likely responsive to venetoclax based on different molecular programs, thus prompting further studies to elucidate better novel potential predictive biomarkers.

Abstract

Mechanisms underlying the pathophysiology of primary Plasma Cell Leukemia (pPCL) and intramedullary multiple myeloma (MM) need to be further elucidated, being potentially relevant for improving therapeutic approaches. In such a context, the MM and pPCL subgroups characterized by t(11;14) deserve a focused investigation, as the presence of the translocation is mainly associated with sensitivity to venetoclax. Herein, we investigated a proprietary cohort of MM and pPCL patients, focusing on the transcriptional signature of samples carrying t(11;14), whose incidence increases in pPCL in association with an unfavorable outcome. In addition, we evaluated the expression levels of the BCL2-gene family members and of a panel of B-cell genes recently reported to be associated with sensitivity to venetoclax in MM. Moreover, transcriptional analysis of lncRNAs in the two clinical settings led to the identification of several differentially expressed transcripts, among which the SNGH6 deregulated lncRNA might be relevant in the pathogenesis and prognosis of pPCL with t(11;14). Overall, our data suggest that MMs and pPCLs with t(11;14) might be responsive to venetoclax based on different molecular programs, prompting further studies to elucidate better novel potential predictive biomarkers.

Leucocytoclastic Vasculitis, Cryoglobulinemia, or Plasma Cell Leukemia: A Diagnostic Conundrum

Plasma cell leukemia is rare and could be life-threatening. Even rarer and equally life-threatening is cryoglobulinemia. Both of them occurring together paints a grim clinical picture. We present the case of a 63-year-old male with plasma cell leukemia complicated by cryoglobulinemia with skin lesions. The report briefly reviews the clinical and diagnostic characteristics of plasma cell leukemia and well as available treatment options. It also highlights the need to consider non-chemotherapy-based regimens and clinical trials in the care of plasma cell leukemia patients.

Necessity of flow cytometry assessment of circulating plasma cells and its connection with clinical characteristics of primary and secondary plasma cell leukaemia

Plasma cell leukaemia (PCL) is a rare and very aggressive plasma cell disorder. Preventing a dismal outcome of PCL requires early diagnosis with appropriate analytical tools. Therefore, the investigation of 33 patients with primary and secondary PCL was done when the quantity of circulating plasma cells (PCs) using flow cytometry (FC) and morphology assessment was evaluated. The phenotypic profile of the PCs was also analysed to determine if there is an association with clinical outcomes and to evaluate the prognostic value of analysed markers. Our results revealed that FC is an excellent method for identifying circulating PCs as a significantly higher number was identified by FC than by morphology (26·7% vs. 13·5%, P = 0·02). None of secondary PCL cases expressed CD19 or CD20. A low level of expression with similar positivity of CD27, CD28, CD81 and CD117 was found in both PCL groups. A decrease of CD44 expression was detected only in secondary PCL. Expression of CD56 was present in more than half of PCL cases as well as cytoplasmic nestin. A decreased level of platelets, Eastern Cooperative Oncology Group score of 2-3 and lack of CD20⁺ PC were associated with a higher risk of death. FC could be incorporated in PCL diagnostics not only to determine the number of circulating PCs, but also to assess their phenotype profile and this information should be useful in patients' diagnosis and possible prognosis.

Venetoclax in combination with chidamide and dexamethasone in relapsed/refractory primary plasma cell leukemia without t(11;14): A case report

BACKGROUND

Conventional therapies for primary plasma cell leukemia (pPCL) are usually ineffective, with a short remission time with the use of multiple myeloma medications, showing aggressiveness of pPCL. B-cell lymphoma-2 inhibitor venetoclax is usually used for relapsed/refractory multiple myeloma (RRMM) with t(11;14). There are very few studies published on the use of venetoclax in pPCL without t(11;14). Similarly, histone deacetylase inhibitors are considered effective for the treatment of RRMM, but there are no reports on their use in pPCL.

CASE SUMMARY

A 57-year-old woman with severe anemia, thrombocytopenia, multiple bone destruction, impaired renal function, and 42.7% of peripheral plasma cells is reported. After multiple chemotherapy regimens and chimeric antigen receptor T-cell treatment, the disease progressed again. The patient had very good partial response and was maintained for a long time on venetoclax in combination with chidamide and dexamethasone therapy.

CONCLUSION

The success of venetoclax-chidamide-dexamethasone combination therapy in achieving a very good partial response suggested that it can be used for refractory/relapsed pPCL patients who have been exhausted with the use of various drug combinations and had poor survival outcomes.

[Prevalence investigation of plasma cell leukemia in China: a calculation based on national urban medical insurance in 2016]

目的

分析我国城市人口中浆细胞白血病（PCL）的流行病学特征，并测算2016年PCL患病率。

方法

利用我国23个省2016年1月1日至2016年12月31日的城镇基本医疗保险数据进行测算。利用医疗保险数据中的疾病诊断名称和疾病诊断编码识别PCL患者。按性别、地区和年龄进行亚组分析，并通过敏感性分析考察结果的稳健性。基于我国2010年全国人口普查数据计算按年龄调整的标准化患病率。

结果

2016年我国城市人口中PCL患病率为0.11/10万（95％CI 0.05～0.19），其中男性和女性患病率分别为0.12/10万（95％CI 0.06～0.21），0.10/10万（95％CI 0.04～0.19）。PCL的患病率在70～79岁时达高峰。敏感性分析显示本研究结果具有稳健性。根据我国2010年全国人口普查数据所得的标化患病率为0.12/10万（95％CI 0.11～0.13）。

结论

本研究首次利用全国城镇医疗保险数据测算我国PCL的患病率，为PCL相关研究和政策制定提供依据。

Risk and Response-Adapted Treatment in Multiple Myeloma

Simple Summary

Therapeutic strategies in multiple myeloma have been adapted only to age and comorbidities for a long time. Given the currently available therapeutic and technologic arsenal, the time may have come to refine this adaptation. First, high-risk patients should benefit from the most intensive and efficient combinations from diagnosis. Here, we review these different strategies and how to define and identify high-risk myeloma patients in current clinical practice. In addition, the advent of technologies detecting minimal residual disease gives us this opportunity to define the quality of response to treatment with an unpreceded sensitivity and adapt treatment accordingly. Finally, even if molecular targeting is still nascent in myeloma, some molecular features are interesting to detect at relapse to determine optimal salvage treatments.

Abstract

Myeloma therapeutic strategies have been adapted to patients’ age and comorbidities for a long time. However, although cytogenetics and clinical presentations (plasmablastic cytology; extramedullary disease) are major prognostic factors, until recently, all patients received the same treatment whatever their initial risk. No strong evidence allows us to use a personalized treatment according to one cytogenetic abnormality in newly diagnosed myeloma. Retrospective studies showed a benefit of a double autologous transplant in high-risk cytogenetics according to the International Myeloma Working Group definition (t(4;14), t(14;16) or del(17p)). Moreover, this definition has to be updated since other independent abnormalities, namely gain 1q, del(1p32), and trisomies 5 or 21, as well as TP53 mutations, are also prognostic. Another very strong predictive tool is the response to treatment assessed by the evaluation of minimal residual disease (MRD). We are convinced that the time has come to use it to adapt the strategy to a dynamic risk. Many trials are ongoing to answer many questions: when and how should we adapt the therapy, its intensity and duration. Nevertheless, we also have to take into account the clinical outcome for one patient, especially adverse events affecting his or her quality of life and his or her preferences for continuous/fixed duration treatment.

Plasma Cell Leukemia - Facts and Controversies: More Questions than Answers?

Plasma cell leukemia (PCL) is an aggressive hematological malignancy characterized by an uncontrolled clonal proliferation of plasma cells (PCs) in the bone marrow and peripheral blood. PCL has been defined by an absolute number of circulating PCs exceeding 2.0 × 10⁹/L and/or >20% PCs in the total leucocyte count. It is classified as primary PCL, which develops de novo, and secondary PCL, occurring at the late and advanced stages of multiple myeloma (MM). Primary and secondary PCL are clinically and biologically two distinct entities. After the diagnosis, treatment should be immediate and should include a proteasome inhibitor and immunomodulator-based combination regimens as induction, followed by stem cell transplantation (SCT) in transplant-eligible individuals who have cleared the peripheral blood of circulating PCs. Due to the rarity of the condition, there have been very few clinical trials. Furthermore, virtually all of the myeloma trials exclude patients with active PCL. The evaluation of response has been defined by the International Myeloma Working Group and consists of both acute leukemia and MM criteria. With conventional chemotherapy, the prognosis of primary PCL has been ominous, with reported overall survival (OS) ranging from 6.8 to 12.6 months. The use of novel agents and autologous SCT appears to be associated with deeper response and an improved survival, although it still remains low. The PCL prognostic index provides a simple score to risk-stratify PCL. The prognosis of secondary PCL is extremely poor, with OS of only 1 month.

Utilizing multiparametric flow cytometry in the diagnosis of patients with primary plasma cell leukemia

The diagnosis of primary plasma cell leukemia (pPCL) has been made by quantifying circulating plasma cells (cPCs) morphologically on a peripheral blood (PB) smear. However, this technique is not sufficiently sensitive. Multiparametric flow cytometry (MFC) provides a readily available and highly sensitive method to identify and quantify cPCs that could complement PB smear assessment. However, an optimal quantitative cutoff for cPCs by MFC to identify pPCL has not been established. Thus, a total of 591 patients newly diagnosed multiple myeloma (NDMM) patients who had their PB samples evaluated morphologically by PB smear, and immunophenotypically by MFC prior to beginning therapy were evaluated. The presence of ≥200 cPCs/μL by MFC (N = 25 or 5% of the total population) was chosen to identify patients with ≥5% cPCs by PB smear with a specificity of 99% and a sensitivity of 77%. For patients with ≥200 cPCs/μL by MFC compared to the remainder of the cohort, the median Time to next therapy (TTNT) was 18 vs 30 months and the median OS was 38 vs 70 months respectively. Thus, MFC assessment of PB can be utilized in conjunction with the morphological assessment of a PB smear to aid in improving the identification of pPCL among NDMM patients.