Myeloma with t(11;14) and CD20+ Plasma Cells: Response to Rituximab.

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 5178-5178
Author(s):  
Patricia T. Greipp ◽  
Rafael Fonseca ◽  
Dewald Dewald ◽  
S. Vincent Rajkumar ◽  
William G. Morice ◽  
...  

Abstract Background: Multiple myeloma (MM) is a plasma cell malignancy involving complex cytogenetic dysregulation of genes and heterogeneous expression of multiple B cell and plasma cell (PC) surface antigens. 60% of MM patients have cytogenetic translocations of the IGH locus. In 16% of myeloma patients, the partner oncogene is cyclin D1 on 11q13 causing t(11;14)(q13;q32) (Fonseca et al. Blood. 2002). This translocation is more common in patients with a lymphoplasmacytic morphology and confers a more favorable prognosis (Fonseca et al. Blood. 2003). A subset of MM patients (20%) harbor a clonotypic population of CD20+ bone marrow plasma cells (BMPC). These patients have a shortened survival time (SanMiguel et al. Br J Haematol. 1991). There is a strong association with CD20+ surface expression and t(11;14)(Robillard et al. Blood. 2003) and CD20+ PC has been suggested to be clonogenic and important in the pathogenesis of MM. A small Phase II study showed only a modest response to the humanized anti-CD20 monoclonal antibody rituximab in MM patients with CD20+PC (1 PR and 5SD) (Treon et al. J. Immunother. 2002). We report a response to treatment with rituximab in a MM patient with CD20+ BMPC and t(11;14)(q13;q32) by FISH. Case: The patient is a 68 year old male with a 1.5 year history of MM. Initial diagnosis of ISS stage I disease was made after a three year history of IgA kappa monoclonal gammopathy of undetermined significance (MGUS). At diagnosis of MM, he had symptomatic anemia Hgb10.5g/dL, rising serum IgA of 3950 mg/dL, serum m-spike of 4.1 g/dL (IgA kappa), PCLI (plasma cell labeling index) of 1%, and a small monoclonal IgA kappa with kappa fragment in the urine. BM showed 44% monoclonal kappa plasma cells with 90% CD20+,clonal PC on flow cytometry. Karyotype was normal; 46, XY, but FISH showed evidence of an IGH translocation t(11;14)(q13;q32) in 60% of PC. Immunohistochemical staining was positive for cyclin D1. Given the marked elevation of CD20+ PC and early stage of disease, initial treatment was employed with four weekly cycles of rituximab (375mg/m2). IgA fell from 4750 mg/dL to a nadir of 2990 mg/dL, (m-spike; 4.5g/dL to 3.2 g/dL) five weeks after completion of treatment. The monoclonal protein (MP) in the urine disappeared. Hgb improved to 12.5g, with erythropoietin. Three months later, IgA rose to 3260mg/dL (m-spike 3.2 g/dL) and urinary MP returned. The patient remained asymptomatic. A second course of weekly rituximab was started. IgA level and serum m-spike remained fairly stable over the next 7 months. All treatment was tolerated well except for initial transient rigors, fever, and nausea. Despite bi-monthly maintenance rituximab, the patient devloped a rising IgA of 4940 mg/dL, m-spike of 4.7, falling Hgb and a rising PCLI of 1.5%, 15 months after his original diagnosis of MM. Of particular concern is the development of new, unfavorable, cytogenetic aberrations by FISH with BMPC now showing deletion 13 in 93% and mutation of p53 (17p13) in 98%.100% show fusion of CCND1 and IGH and PC now only partially express CD20. Conclusion: This report suggests that MM patients with CD20+ BMPC and t(11;14)(q13;q32) may represent a target population for anti-CD20 therapy. Our report supports the concept proposed that targeting this clonotypic subset of B cells possibly interrupts a critical oncogenic pathway that is important in the pathogenesis of the clonogenic development of MM.

Blood ◽  
2002 ◽  
Vol 99 (10) ◽  
pp. 3735-3741 ◽  
Author(s):  
Rafael Fonseca ◽  
Emily A. Blood ◽  
Martin M. Oken ◽  
Robert A. Kyle ◽  
Gordon W. Dewald ◽  
...  

The t(11;14)(q13;q32) results in up-regulation of cyclin D1 and is the most common translocation detected in multiple myeloma, where it is also associated with a lymphoplasmacytic morphology. We performed an interphase fluorescent in situ hybridization (FISH) study to determine the clinical and biologic significance of the abnormality when testing a large cohort of myeloma patients. Bone marrow slides from multiple myeloma patients entered into the Eastern Cooperative Oncology Group phase III clinical trial E9486 and associated laboratory correlative study E9487 were analyzed using interphase FISH combined with immune-fluorescent (cytoplasmic immunoglobulin–FISH) detection of clonal plasma cells. We used FISH probes that hybridize to the 14q32 and 11q13 chromosomal loci. The t(11;14)(q13;q32) was correlated with known biologic and prognostic factors. Of 336 evaluable patients, 53 (16%) had abnormal FISH patterns compatible with the t(11;14)(q13;q32). These patients appeared to be more likely to have a serum monoclonal protein of less than 10 g/L (1 g/dL) (28% vs 15%, P = .029) and a lower plasma cell labeling index (P = .09). More strikingly, patients were less likely to be hyperdiploid by DNA content analysis (n = 251, 14% vs 62%, P < .001). Patients with the t(11;14)(q13;q32) appeared to have better survival and response to treatment, although this did not reach statistical significance. Multiple myeloma with the t(11;14)(q13;q32) is a unique subset of patients, not only characterized by cyclin D1 up-regulation and a lymphoplasmacytic morphology, but is also more frequently associated with small serum monoclonal proteins and is much less likely to be hyperdiploid. These patients do not have a worsened prognosis as previously thought.


2007 ◽  
Vol 8 (4) ◽  
pp. 60-66 ◽  
Author(s):  
Sukumaran Anil

Abstract Aim The aim of this article is to present a brief review of plasma cell gingivitis (PCG) along with reports of three cases with varying clinical presentations of the condition associated with the use of herbal toothpaste. Background PCG is a rare benign condition of the gingiva characterized by sharply demarcated erythematous and edematous gingivitis often extending to the mucogingival junction. This is considered a hypersensitive reaction. The histological appearance consists of a dense infiltration of normal plasma cells separated by collagenous stroma, usually confined to the free and attached gingiva. The lesion can be eliminated by identifying and avoiding the source of the allergen. Report Three patients ages 26, 27, and 36, respectively, presented with acutely inflamed gingival and a history of recently switching to herbal toothpaste. The gingiva bled readily on probing. Blood tests and gingival biopsy were not contributory. Patients were advised to refrain from the use of herbal toothpaste, and, along with periodontal treatment, the condition underwent remission within a week to two weeks in all three cases. Summary As more and more herbal products are gaining popularity, clinicians should be aware of some of the untoward effects of these products. Since PCG mimics lesions associated with leukemia and myeloma an early diagnosis of the condition is vital. Citation Anil S. Plasma Cell Gingivitis Among Herbal Toothpaste Users: A Report of Three Cases. J Contemp Dent Pract 2007 May;(8)4:060-066.


Blood ◽  
2007 ◽  
Vol 109 (11) ◽  
pp. 4856-4864 ◽  
Author(s):  
David R. Withers ◽  
Claudia Fiorini ◽  
Randy T. Fischer ◽  
Rachel Ettinger ◽  
Peter E. Lipsky ◽  
...  

Abstract The signals mediating human plasma cell survival in vivo, particularly within secondary lymphoid tissue, are unclear. Human tonsils grafted into immunodeficient mice were therefore used to delineate the mechanisms promoting the survival of plasma cells. Tonsillar plasma cells were maintained within the grafts and the majority were nonproliferating, indicating a long-lived phenotype. A significant depletion of graft plasma cells was observed after anti-CD20 treatment, consistent with the expression of CD20 by most of the cells. Moreover, anti-CD52 treatment caused the complete loss of all graft lymphocytes, including plasma cells. Unexpectedly, anti-CD3, but not anti-CD154, treatment caused the complete loss of plasma cells, indicating an essential role for T cells, but not CD40-CD154 interactions in plasma cell survival. The in vitro coculture of purified tonsillar plasma cells and T cells revealed a T-cell survival signal requiring cell contact. Furthermore, immunofluorescence studies detected a close association between human plasma cells and T cells in vivo. These data reveal that human tonsil contains long-lived plasma cells, the majority of which express CD20 and can be deleted with anti-CD20 therapy. In addition, an important role for contact-dependent interactions with T cells in human plasma cell survival within secondary lymphoid tissue was identified.


Blood ◽  
2011 ◽  
Vol 118 (10) ◽  
pp. 2702-2707 ◽  
Author(s):  
Jeremy T. Larsen ◽  
Cheng E. Chee ◽  
John A. Lust ◽  
Philip R. Greipp ◽  
S. Vincent Rajkumar

Abstract Standard myeloma treatment response criteria are determined principally by changes in the monoclonal protein. Reduction in the size of the proliferative component of malignant plasma cells may be an additional metric of assessing response to therapy. We retrospectively analyzed 176 patients with newly diagnosed myeloma with a measurable plasma cell labeling index (PCLI) at diagnosis and repeat measurement 4 months after initiation of therapy. PCLI response was defined as a ≥ 60% reduction. Baseline PCLI is an independent prognostic factor; therefore, we categorized patients into 3 groups: PCLI ≥ 3% (high), ≥ 1% (intermediate), and < 1% (low). Patients achieving a greater PCLI response had improved median overall survival of 54 months compared with 29 months in nonresponders (P = .02). Improved median overall survival with PCLI response occurred in the high initial PCLI group (28 vs 7 months; P = .003) and intermediate group (64 vs 24 months; P = .002). The application of PCLI response and serum M-spike response together provided further prognostic information. On multivariate analysis, the prognostic value of PCLI response was independent of β2-microglobulin, elevated creatinine, serum M-spike response, and baseline PCLI. We conclude that a significant reduction in plasma cell proliferation in patients with newly diagnosed myeloma is an important predictor of survival.


Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 4854-4854
Author(s):  
James R. Cook ◽  
Eric D. Hsi ◽  
Raymond R. Tubbs ◽  
Sarah Worley ◽  
Mohamad A. Hussein

Abstract The expression of Cyclin D1 is dysregulated in approximately half of cases of plasma cell myeloma due to translocations, aneusomy, or other abnormalities. Recent studies using quantitative mRNA analysis have suggested that increased Cyclin D1 mRNA expression is associated with a favorable prognosis. Previous attempts to examine the significance of cyclin D1 protein expression by immunohistochemistry have been hampered by the use of antibodies with weak staining and high background. In this study, we employ a newly available, commercial antibody that gives superior staining in B5 fixed tissues. We performed immunohistochemistry for Cyclin D1 on bone marrow core biopsies from a series of 44 newly diagnosed plasma cell myeloma patients who were uniformly treated on a Phase II study of rituxan, melphalan and prednisone. 22 patients (50%) were positive for Cyclin D1, defined as any plasma cells with positive nuclear staining. Cyclin D1 positive and negative cases displayed no significant differences in the initial levels of β2m (3.6±0.5 mg/L vs. 3.5±0.5 mg/L, p=0.860), number of bone marrow plasma cells (63±5.5% vs. 47±6.2%, p=0.063), or proportion of cases classified as SWOG stage 3-4 (2 of 22 (9%) vs. 5 of 22 (23%), p=0.412). The cyclin D1 positive cases displayed a superior overall survival with an estimated 3-year survival of 95% for Cyclin D1 positive cases versus 56% for Cyclin D1 negative cases (p=0.032). The cyclin D1 positive cases also displayed a trend towards better progression-free survival (median progression free survival of 15.7 months for Cyclin D1 positive versus 12.8 months for Cyclin D1 negative, p=0.13). In a Cox proportional hazards regression model, used to compare the effect of Cyclin D1 protein expression on overall survival time while adjusting for stage, the Cyclin D1 positive patients continued to show a strong trend to better overall survival (p=0.062). This study demonstrates that cyclin D1 immunohistochemistry, which could be readily performed in most pathology laboratories, is capable of identifying a subset of plasma cell myeloma with a favorable survival. Additional studies are ongoing to determine if these results can be generalized to other forms of therapy. If confirmed, routine cyclin D1 immunohistochemistry at the time of diagnosis may offer important prognostic information that could identify lower risk patients for whom less intensive therapies might be appropriate.


Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 3396-3396 ◽  
Author(s):  
Robert Kyle ◽  
Ellen Remstein ◽  
Terry Therneau ◽  
Angela Dispenzieri ◽  
Paul Kurtin ◽  
...  

Abstract Smoldering multiple myeloma (SMM) is characterized by a serum M protein ≥ 3g/dL and/or 10% or more of plasma cells in the bone marrow. However, the definition is not standardized, and it is not known whether both serum M protein levels and bone marrow plasma cell counts are necessary for diagnosis or if one parameter is sufficient. We reviewed the medical records and bone marrows of all patients from Mayo Clinic seen within 30 days of recognition of an IgG or IgA M protein ≥ 3g/dL or a bone marrow containing ≥ 10% plasma cells from 1970 to 1995. This allows for a minimum potential follow-up of 10 years. Patients with end-organ damage at baseline from plasma cell proliferation, including active multiple myeloma (MM) and primary amyloidosis (AL) and those who had received chemotherapy were excluded. A differential of the bone marrow aspirate coupled with the bone marrow biopsy morphology and immunohistochemistry using antibodies directed against CD138, MUM-1 and Cyclin D1 were evaluated in every case in order to estimate the plasma cell content. In all, 301 patients fulfilled either of the criteria for SMM. Their median age was 64 years and only 3% were less than 40 years of age; 60% were male. The median hemoglobin value was 12.9 g/dL; 7% were less than 10 g/dL, but the anemia was unrelated to plasma cell proliferation. IgG accounted for 75%, IgA 22%, and biclonal proteins were found in 3%. The serum light-chain was κ in 67% and λ in 33%. The median serum M spike was 2.9 g/dL; 11% were at least 4.0 g/dL. Uninvolved serum immunoglobulins were reduced in 81%; only 1 immunoglobulin was reduced in 31% and both were decreased in 50%. The urine contained a monoclonal κ protein in 36% and λ in 18% and 46% were negative. The median size of the urine M spike was 0.04 g/24h; only 5 (3%) were &gt; 1 g/24h. The median bone marrow plasma cell content was 15 – 19%; 10% had less than 10% plasma cells, while 10% had at least 50% plasma cells in the bone marrow. Cyclin D-1 was expressed in 17%. Patients were categorized into 3 groups: Group 1, serum M protein ≥ 3g/dL and bone marrow containing ≥ 10% plasma cells (n= 113, 38%); Group 2, bone marrow plasma cells ≥ 10% but serum M protein &lt; 3g/dL (n= 158, 52%); Group 3, serum M protein ≥ 3g/dL but bone marrow plasma cells &lt; 10% (n= 30, 10%). During 2,204 cumulative years of follow-up 85% died (median follow-up of those still living 10.8 years), 155 (51%) developed MM, while 7 (2%) developed AL. The overall rate of progression at 10 years was 62%; median time to progression was 5.5 yrs. The median time to progression was 2.4, 9.2, and 19 years in groups 1, 2, and 3 respectively; correspondingly at 10 years, progression occurred in 76%, 59%, and 32% respectively. Significant risk factors for progression with univariate analysis were serum M spike ≥ 4g/dL (p &lt; 0.001), presence of IgA (p = 0.003), presence of urine light chain (p = 0.006), presence of λ urinary light chain (p = 0.002), bone marrow plasma cells ≥ 20% (p &lt; 0.001) and reduction of uninvolved immunoglobulins (p &lt; 0.001). The hemoglobin value, gender, serum albumin, and expression of cyclin D-1 were not of prognostic importance. On multivariate analysis, the percentage of bone marrow plasma cells was the only significant factor predicting progression to MM or AL.


Blood ◽  
2012 ◽  
Vol 120 (21) ◽  
pp. 1874-1874
Author(s):  
Kathleen A. Donovan ◽  
Laurie L. Moon-Tasson ◽  
John A Lust

Abstract Abstract 1874 In early stage myeloma, IL-6 is a central myeloma growth factor and we have shown that abnormal production of IL-1 in the myeloma microenvironment stimulates the generation of IL-6 in a paracrine fashion. IL-1 has also been shown to be a crucial factor in the induction of IL-17 producing T-cells in vivo. IL-1Ra is a specific blocker of IL-1 activity. We have previously reported on a Phase II trial using IL-1Ra and dexamethasone, in patients with smoldering/indolent MM (SMM/IMM), showing that IL-1Ra targets the myeloma proliferative component which parallels a decrease in the C-reactive protein (CRP), a surrogate for IL-6 production. These patients are the individuals most likely to benefit from anti-cytokine therapy in an attempt to delay/prevent the development of active myeloma. Patients that had > 10% bone marrow plasma cells and/or an IgG or IgA M-spike > 3 g/dL and did not require immediate chemotherapy were eligible. All patients received 100 mg of Anakinra (IL-1Ra) SQ qd for 6 months. Patients with evidence of reduction in M-protein levels continued receiving IL-1Ra alone. Patients with stable disease at 6 months or those with a rising M-protein before 6 months received low dose dexamethasone (20 mg qweek) in addition; the dose was adjusted based on response/toxicity. Data were available on 47 patients based on intent to treat, and patients were classified as smoldering (72%) vs. indolent (28%). All 47 patients received IL-1Ra initially and 25/47 subsequently received IL-1Ra/Dex. Myeloma cell growth rate (PCLI), C-reactive protein (an in vivo marker of IL-6 levels) and IL-17 were measured in patients on trial. Seven patients had a decrease in the plasma cell labeling index (PCLI) on IL-1Ra alone which paralleled a decrease in the C-reactive protein in all cases. Three patients achieved a minor response to IL-1Ra alone and 9 patients achieved a PR/MR after addition of dexamethasone. When patients were grouped into whether they exhibited a reduction in the C-reactive protein from baseline after 6 months of therapy, the median PFS for patients without (21 patients) or with (26 patients) a greater than one-third reduction in baseline CRP was 1 year vs more than 8 years (p<.01). Analyses of biomarkers suggest that patients with elevated IL-17 levels may be less likely to respond to IL-1Ra treatment. Only 25% of the responders with a decrease in CRP had IL-17 levels > 10 pg/ml versus 60% of those without a CRP decrease. Although not statistically significant do to the small sample size, the median PFS in the IL-17 < 10 pg/ml group was 2047days vs 1367 days in the IL-17 > 10 pg/ml group. In conclusion, the above results suggest that agents such as IL-1Ra that specifically inhibit IL-1 induced paracrine IL-6 production are effective at targeting the proliferative myeloma component and warrant further investigation in combination with standard myeloma therapies. Elevated IL-17 levels may suggest that the inflammatory process is too far advanced in some individuals to respond to IL-1 blockade. Biomarkers such as CRP and IL-17 may be useful to predict those patients that are most likely to benefit from IL-1 treatment. Disclosures: Off Label Use: IL-1Ra in myeloma.


Blood ◽  
2013 ◽  
Vol 122 (21) ◽  
pp. 5319-5319
Author(s):  
Daniela Lakomy ◽  
Stephanie Lemaire-Ewing ◽  
Cedric Rossi ◽  
Jessica Borgeot ◽  
Jean-Noël Bastie ◽  
...  

Abstract Introduction The evaluation of multiple myeloma response to treatment as defined by international guidelines is currently based on morphologic examination of bone marrow plasma cells, serum protein electrophoresis (SPEP), immunofixation electrophoresis (IFE) and serum free light chain assay. For several years new tools are available as bone marrow plasma cell immunophenotyping and the HevyliteTM assay. HevyliteTM IgA assay provides an automated evaluation of serum heavy/light chain ratio (HLC) of the involved and uninvolved immunoglobulin (Ig) (i.e. IgAΚ/IgAλ). This is particularly interesting in IgA myeloma where the use of SPEP is limited due to a frequent comigration of monoclonal IgA with other proteins. We therefore compared the IgA quantification by Hevylite™ assay and the bone marrow plasma cell immunophenotyping for response evaluation and residual disease characterisation in IgA myeloma. Methods Hevylite™ assay, SPEP, IFE were performed in eleven IgA myeloma patients at different times: after induction chemotherapy, after the consolidation phase and after autologous stem-cell transplantation (ASCT). In the same time, minimal residual disease (MRD) assessment was performed on bone marrrow by multiparameter flow cytometry (MFC). Hevylite™ assay was performed on a Binding Site SPAplus analyser (Hevylite, Binding Site, Birmingham, UK) following the manufacturer recommendations. SPE and IFE were realized on Sebia Hydrasys analyser (Sebia, Evry, France) and results were read by two experienced biologists. Results 1. We found a perfect agreement between the IFE and immunophenotyping results at each time of evaluation, for positive results as for negative results. 2. The SPEP was contributive only in two patients and in these cases it was less sensitive than IFE. In the other patients, the monoclonal IgA migrated in beta region and/or as multiple bands, making the quantitative estimation difficult. 3. In all patients, when MRD by MFC was undetectable and IFE was negative, the HLC ratio was normal. 4. In 3 patients, HLC ratio was consistent with the IFE and MRD by MFC at each time of evaluation. Nevertheless, in 8 patients out of 11, while HLC ratio became normal, MRD by MFC and IFE were still positive. In all cases, the normalization of HLC ratio was followed, at the next step of evaluation, by the normalization of MFC and IFE. 5. In 5 patients, the normalization of HLC ratio occurred before ASCT, while IFE and MRD by MFC were still positive. Nevertheless, after ASCT, IFE and MRD by MFC became also negative, in accordance with the HLC ratio (Table 1). Conclusions During the evaluation of response to treatment of IgA myeloma, we observed a normalization of HLC ratio (Hevylite™ IgA assay) preceding the normalization of MRD by MFC and IFE. This could be explained by the fact that IFE and immunophenotyping provide very sensitive information but only on the monoclonal component. HLC ratio reflects the balance between the monoclonal and polyclonal Igs of involved and uninvolved isotype. A normalization of HLC ratio can be interpreted as an increasing polyclonal Ig proportion parallel with a decreasing monoclonal Ig proportion and may reflect the reconstitution of polyclonal plasma cells. If confirmed by other studies and long term follow-up, HLC ratio could be a non-invasive predictive marker of a good response in IgA myeloma. Disclosures: No relevant conflicts of interest to declare.


Blood ◽  
2001 ◽  
Vol 97 (8) ◽  
pp. 2522-2523 ◽  
Author(s):  
David P. Steensma ◽  
Morie A. Gertz ◽  
Philip R. Greipp ◽  
Robert A. Kyle ◽  
Martha Q. Lacy ◽  
...  

Abstract The plasma cell labeling index (PCLI) is a measure of plasma cell proliferative activity and is an important prognostic factor in newly diagnosed multiple myeloma (MM). Occasionally patients have been observed with stable, plateau phase MM with minimal numbers of residual light-chain–restricted monoclonal plasma cells, but a high PCLI. No data are available on the outcomes for such patients. Data from 57 patients with plateau phase MM and a marrow PCLI of more than 1.0% were compared with 105 matched control patients with MM with a marrow PCLI of less than 1.0%. All patients had less than 10% total plasma cells on marrow aspirate and biopsy. The median time to progression and overall survival were 8 months and 20 months, respectively, in the high PCLI group versus 39 months and 56 months, respectively, in the low PCLI group (P &lt; .0001). These findings suggest that a high PCLI in patients with apparently stable, plateau phase MM is an adverse parameter that may predict a short time to disease progression and death.


Blood ◽  
2016 ◽  
Vol 128 (22) ◽  
pp. 5630-5630 ◽  
Author(s):  
Sudhir Perincheri ◽  
Richard Torres ◽  
Christopher A Tormey ◽  
Brian R Smith ◽  
Henry M Rinder ◽  
...  

Abstract The diagnosis of multiple myeloma (MM) requires the demonstration of clonal plasma cells at ≥10% marrow cellularity or a biopsy-proven bony or extra-medullary plasmacytoma, plus one or more myeloma-defining events. Clinical laboratories use multi-parameter flow cytometry (MFC) evaluation of cytoplasmic light chain expression in CD38-bright, CD45-dim or CD138-positive, CD45dim cells to establish plasma cell clonality with a high-degree of sensitivity and specificity. Daratumumab, a humanized IgG1 kappa monoclonal antibody targeting CD38, has been shown to significantly improve outcomes in refractory MM, and daratumumab was granted breakthrough status in 2013. Daratumumab is currently approved for treatment of MM patients who have failed first-line therapies. It has been noted that daratumumab can interfere in blood bank assays for antibody screening, as well as serum protein electrophoresis (SPEP). We describe for the first time daratumumab interference in the assessment of plasma cell neoplasms by MFC; daratumumab interfered with both CD38- and CD138-based gating strategies in three MM patients. Patient A is a 68 year old man with a 10 year history of MM who had failed multiple therapies. He had then been treated with daratumumab for two months, stopping therapy 25 days prior to bone marrow assessment. Patient B is a 53 year old man with a 3 year history MM who had failed numerous treatments. He had been receiving daratumumab monotherapy for two months at the time of his bone marrow studies. On multiple marrow aspirates at times of relapse prior to receiving daratumumab, both patients had demonstrated CD38-bright positive CD45dim/negative plasma cells expressing aberrant CD56, as well as kappa light chain restriction; mature B cells were polyclonal in both. Patient C is a 65 year old man with a four-year history of MM status post autologous stem cell transplantation, who had been receiving carfilzomib and pomalidomide following relapse and continues to have rising lambda light chains and rib pain. He now has abnormal plasma cells in blood worrisome for plasma cell leukemia. Bone marrow aspirates from patients A and B, and blood from patient C demonstrated near absence of CD38-bright events as detected by MFC (Figure 1). Hypothesizing that these results were due to blocking of the CD38 antigen by daratumumab, gating on CD138-positive events was assessed; surprisingly, virtually no CD138-positive events were detected by MFC. All 3 samples demonstrated a CD56-positive CD45dim population; when light chain studies were employed using specific gating on the CD56-positive population, light chain restriction was demonstrated in all patients (Figure 1). Aspirate morphology confirmed numerous abnormal, nucleolated plasma cells (Figure 2A), thus excluding a sampling error. CD138 and CD38 expression was also tested on the marrow biopsy cores from both patients. In contrast to MFC, immunohistochemistry (IHC) showed positive labeling of plasma cells with both CD138 (Figure 2B) and CD38 (Figure 2C). The reason for the labeling discrepancy between MFC and IHC is unknown. The different antibodies in the assays may target different epitopes; alternatively, tissue fixation/decalcification may dissociate the anti-CD38 therapeutic monoclonal from its target. Detection of clonal plasma cell populations is important for assessing response to therapy. Laboratories relying primarily on MFC to assess marrow aspirates without a concomitant biopsy may falsely diagnose remission or significant disease amelioration in daratumumab-treated patients. MFC is generally highly sensitive for monitoring minimal residual disease (MRD) in MM, but daratumumab-treated patients should have their biopsy evaluated to confirm the MRD assessment by MFC. We were able to detect large numbers of plasma cells and also demonstrate clonality in our patients based on an alternative MFC marker, aberrant CD56 expression, an approach that may not be possible in all cases. Figure 1 Flow cytometry showing near-absence of CD38-bright elements in the marrow of patient A (top panels). Gating on CD56-positive cells in the same sample reveals a kappa light chain-restricted plasma cell population (bottom panels). Figure 1. Flow cytometry showing near-absence of CD38-bright elements in the marrow of patient A (top panels). Gating on CD56-positive cells in the same sample reveals a kappa light chain-restricted plasma cell population (bottom panels). Figure 1 The marrow aspirate from Fig. 1 shows abnormal plasma cells (A). Immunohistochemistry on the concomitant biopsy shows the presence of numerous CD138-positive (B) and CD38-positive (C) plasma cells. Figure 1. The marrow aspirate from Fig. 1 shows abnormal plasma cells (A). Immunohistochemistry on the concomitant biopsy shows the presence of numerous CD138-positive (B) and CD38-positive (C) plasma cells. Disclosures No relevant conflicts of interest to declare.


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