High-risk multiple myeloma predicted by circulating plasma cells and its genetic characteristics

A review on pathobiology of circulating tumour plasma cells: The sine qua non of poor prognosis in plasma cell neoplasms

Circulating plasma cells (CPCs) in patients of plasma cell neoplasm have been an area of intense research in recent decades. Circulating tumor plasma cells (CTPCs) might represent a sub-clone of tumor cells that have exited into peripheral blood as a result of the dynamic interactions between the bone marrow (BM) microenvironment and neoplastic plasma cells. Chemokine receptors like chemokine receptor 4 (CXCR4) and integrins are known to play a role in homing and migration of plasma cells (PCs). The hypoxic microenvironment in the BM niche also contributes to their circulation through various mechanisms. In addition, the CCL3-CCR1 axis probably competes with the retention signals from the CXCR4-α4β1 (VLA-4) interaction and actively promotes the exit of PCs from the BM. CTPCs, even in extremely low numbers, can be detected and quantified by high-sensitivity techniques like multi-color flow cytometry and next-generation sequencing. High load of CTPCs noted in patients of plasma cell neoplasm; monoclonal gammopathy of undetermined significance (MGUS), smoldering multiple myeloma (SMM), multiple myeloma (MM) is a strong predictor of shorter progression free survival (PFS) as well as overall survival (OS). In newly diagnosed patients of MM, a load of CTPCs correlates with the outcomes, i.e., OS and PFS. With more studies collaborating on the results of previous reports, assessment of the burden of CTPCs may become a complimentary approach for non-invasive risk stratification of MM patients and evaluating the response to therapy. Future research on larger cohorts and longer follow-ups may help to improve the existing staging system by incorporating the load of CTPCs as one of the prognostic indicators. Further studies based on isolation and genetic characterization of CTPCs may help in understanding the pathophysiology of the progression of the disease and may open avenues for newer treatment modalities. This review discusses the pathobiological aspects leading to circulation of neoplastic/tumor plasma cells in peripheral blood and provides a summary of research work done in last two decades on its prognostic importance in various plasma cells neoplasms.

Circulating plasma cells as a predictive biomarker in Multiple myeloma: an updated systematic review and meta-analysis

BACKGROUND

Circulating plasma cells (CPCs) are defined by the presence of peripheral blood clonal plasma cells, which would contribute to the progression and dissemination of multiple myeloma (MM). An increasing number of studies have demonstrated the predictive potential of CPCs in the past few years. Therefore, there is a growing need for an updated meta-analysis to identify the specific relationship between CPCs and the prognosis of MM based on the current research status.

METHODS

The PubMed, Embase, and Cochrane Library databases were screened to determine eligible studies from inception to November 5, 2023. Publications that reported the prognostic value of CPCs in MM patients were included. Hazard ratios (HRs) with 95% confidence intervals (CIs) of overall survival (OS) and progression-free survival (PFS) were extracted to pool the results. Subgroup analyses were performed based on region, sample size, cut-off value, detection time, initial treatment, and data type. The association between CPCs level and clinicopathological characteristics, including the International Staging System (ISS), Revised-ISS (R-ISS), and cytogenetic abnormalities were also evaluated. Statistical analyses were conducted using STATA 17.0 software.

RESULTS

Twenty-two studies with a total of 5637 myeloma patients were enrolled in the current meta-analysis. The results indicated that myeloma patients with elevated CPCs were expected to have a poor OS (HR = 2.19, 95% CI: 1.81-2.66, p < 0.001) and PFS (HR = 2.45, 95% CI: 1.93-3.12, p < 0.001). Subgroup analyses did not alter the prognostic role of CPCs, regardless of region, sample size, cut-off value, detection time, initial treatment, or data type. Moreover, the increased CPCs were significantly related to advanced tumour stage (ISS III vs. ISS I-II: pooled OR = 2.89, 95% CI: 2.41-3.46, p < 0.001; R-ISS III vs. R-ISS I-II: pooled OR = 3.65, 95% CI: 2.43-5.50, p < 0.001) and high-risk cytogenetics (high-risk vs. standard-risk: OR = 2.22, 95% CI: 1.60-3.08, p < 0.001).

CONCLUSION

Our meta-analysis confirmed that the increased number of CPCs had a negative impact on the PFS and OS of MM patients. Therefore, CPCs could be a promising prognostic biomarker that helps with risk stratification and disease monitoring.

Detection of circulating normal and tumor plasma cells in newly diagnosed patients of multiple myeloma and their associations with clinical and laboratory parameters

INTRODUCTION

Circulating plasma cells (CPCs) are frequently noted in variable frequencies in the entire spectrum of plasma cells neoplasms. With advent of high sensitivity multi-parametric flow cytometry, it is not only possible to detect CPCs present in very low numbers, but also to categorise them into circulating tumor plasma cells (CTPCs) and circulating normal plasma cells (CNPCs), based on their marker-profile. This study used multi-colour flow cytometry to evaluate the load of both CTPCs & CNPCs at the time of diagnosis and at six months' time-point of therapy, and evaluated associations of both with clinical and laboratory parameters.

METHODS

Twenty one newly diagnosed MM patients were enrolled. Six to nine millilitres of EDTA-anticoagulated peripheral blood sample was used for flow cytometry. A ten colour antibody panel was used for analysis of CPCs, which were categorised further into CTPCs and CNPCs. Approximately 4.8 million events were acquired for the analysis. The percentage &absolute numbers of CTPCs and CNPCs were noted and the proportion of CTPCs out of all CPCs (CTPCs + CNPCs) were also calculated for evaluating their statistical associations.

RESULTS

All 21 patients of newly diagnosed MM showed presence of CPCs (CTPCs and/or CNPCs) at the time of diagnosis. The CTPCs were detected in 76 % of the study population. The median percentage and absolute counts of CTPCs were 0.52 % and 54.9 cells /µL, respectively. CNPCs were found in 95 % and the median percentage and absolute counts of CNPCs were 0.025 % and 2.66 cells/µL. After six months of therapy, CPCs (CTPCs and/or CNPCs) were found in all nine patients evaluated for this assay. CTPCs were found 33 %, with a median of 0.075 % and CNPCs were found in 89 % with a median of 0.01 %. Our study showed that the load of CTPCs was found to be higher in patients with presence of lytic bone lesions, plasmacytoma, presence of PCs on peripheral blood film by light microscopy, presence of Chr 1p32 deletion, expression of CD56 and CD81 on CTPCs, and in patients with absence of very good partial response (VGPR). Conversely, the load of CTPCs was significantly lower in patients with concomitant amyloidosis. Also, percentage of bone marrow plasma cells exhibited a significant positive correlation with the absolute count of CTPCs. We observed that the mean percentage of CNPCs was significantly higher in female patients. The load of CNPCs was lower in patients with thrombocytopenia and with hypoalbuminemia.

CONCLUSION

Increased burden of CTPCs was associated with presence of lytic lesions, plasmacytomas, Chr 1p32 deletion, expression of CD56 and CD81 on tumor cells and with failure to achieve very good partial response. The CNPCs were lower in patients with thrombocytopenia and with hypoalbuminemia. To best ot our knowledge, this is the first study from India on the relevance of circulating tumor plasma cells and the first study in the world to analyse the associations of circulating normal plasma cells in newly diagnosed patients of multiple myeloma. The study also highlights the utility of multi-parametric flow cytometry in identification and enumeration of circulating plasma cells.

MICRO ABSTRACT

Circulating plasma cells indicates poorer outcomes in patients of multiple myeloma. Twenty one newly diagnosed multiple myeloma patients were evaluated by flow cytometry to enumerate and characterise circulating tumor plasma cells (CTPCs) and circulating normal plasma cells (CNPCs). Higher load of CTPCs correlated with known poor prognostic markers and poor response to therapy.

Definers and drivers of functional high-risk multiple myeloma: insights from genomic, transcriptomic, and immune profiling

Traditional prognostic models for newly diagnosed patients with multiple myeloma (MM), including International Staging System criteria and number of high-risk chromosomal abnormalities, are based on disease characteristics at diagnosis. However, the identification of patients at risk of more rapidly progressive MM is inherently a dynamic assessment. In a subset of patients with MM, adverse disease biology only becomes evident after the failure of first-line therapy. We define this entity as functional high-risk MM (FHRMM), encompassing relapse within 18 months of treatment initiation and/or within 12 months of frontline autologous stem cell transplantation. FHRMM is not adequately captured by traditional prognostic models, and there is a need for better understanding of mechanisms or risk factors for early relapse or progression. In this review, we explore potential definitions of FHRMM before delving into its underlying drivers based on genetic, transcriptomic, and immune cell profiling studies. Emerging data suggest that specific features of both myeloma cells and immune cells can enable the FHRMM phenotype. We conclude our review by discussing ongoing and future studies that seek to identify and intervene upon patients with FHRMM preemptively.