Reduction In Proliferative Rate of Myeloma Plasma Cells Measured by the Plasma Cell Labeling Index Predicts Improved Survival In Multiple Myeloma

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 4048-4048
Author(s):  
Jeremy T Larsen ◽  
Cheng E. Chee ◽  
John Lust ◽  
Philip R. Greipp ◽  
S. Vincent Rajkumar

Abstract Abstract 4048 Background: The plasma cell labeling index (PCLI) is measured as the percentage of bone marrow plasma cells (PC) in the S phase of the cell cycle and provides an estimate of the proliferative capacity of malignant PC in multiple myeloma (MM). The International Myeloma Working Group (IMWG) uniform response criteria measure the monoclonal (M) protein and serum free light chain (FLC) assay to evaluate clinical response. An elevated PCLI is an established adverse prognostic risk factor for survival, however it is unknown if the PCLI response to therapy offers further prognostic value. Methods: Data from 176 newly diagnosed MM patients from 1985 to 2005 were collected from the Mayo Clinic dysproteinemia database. Inclusion criteria for the study required a minimum initial PCLI of 0.5% and a subsequent PCLI 4 months after initiation of therapy. Baseline and subsequent serum M-protein, progression date, and overall survival were recorded. Clinical responses were assessed by the IMWG uniform response criteria. The association of PCLI response and treatment response (CR, VGPR, or PR) was assessed univariately. Overall survival based on PCLI response, M-spike reduction, and treatment response by IMWG criteria was estimated using the Kaplan-Meier method. Results: The median overall survival (OS) was 47 months (range: 4 – 165). Ninety-four patients (53%) demonstrated a ≥60% reduction in PCLI after initial therapy (responders) and this conferred a significant OS advantage of 51 months vs. 34 months (P<0.01; Figure 1) compared to those who achieved <60% PCLI reduction (non-responders) after initial therapy. The median PCLI percent difference following 4 months of therapy was -67% (+/− 137%; range: -100 to 953%). When patients were stratified into high (PCLI of ≥3%), intermediate (PCLI ≥1%) and low (PCLI <1%) risk groups, OS was significantly improved in the high and intermediate PCLI groups if they achieved ≥60% reduction in PCLI after initial therapy, 31 vs. 7 months (P<0.0022; Figure 2) and 63 vs. 25 months (P<0.0005; Figure 3), respectively. As observed in prior studies, patients with PCLI of ≥3% at diagnosis had shorter overall survival (17 months) when compared to patients with an initial PCLI of <1% (61 months; P < 0.0001). Of the 94 responders, 39% (n=37) did not achieve a response to therapy as measured by M-protein. Thirteen patients (14%) had no measurable serum M-protein at baseline. Conversely, 35% (n=31) of patients that responded by M-protein criteria did not achieve a PCLI response. In patients who achieved CR/PR after 4 months of therapy, the median PCLI reduction was 83.7% vs. 22.5% (P <0.0004) compared to patients with stable disease (not meeting criteria for CR or PR) or progressive disease (as specified by IMWG response criteria). This reflects a significant reduction in disease burden and as expected, median OS was better in the CR/PR group (53 vs. 31 months, P <0.0016). Conclusion: Our study demonstrates that the degree of PCLI reduction after therapy is important in predicting overall survival and response to therapy. This is an important finding in the current setting of effective MM treatment options, whereby patients who do not achieve an adequate response as defined as ≥60% reduction in PCLI in our study, may require change in therapy. Our data confirm that reduction of M-protein is an important surrogate endpoint, as patients who achieved PR and CR lived significantly longer. A significant portion of individuals 39% had a measurable response by PCLI that was not detected by M-protein. Further studies are needed to evaluate the predictive value of the addition a criterion that looks at reduction in proliferative rate as measured by PCLI or other methods such as flow cytometry. Disclosures: Greipp: Mayo Clinic: Patents & Royalties.

Blood ◽  
2015 ◽  
Vol 126 (23) ◽  
pp. 2991-2991
Author(s):  
Peter A. Forsberg ◽  
Tomer M Mark ◽  
Sujitha Yadlapati ◽  
Adriana C Rossi ◽  
Roger N Pearse ◽  
...  

Abstract Background: Assessment of malignant plasma cell cycling via plasma cell labeling index (PCLI) has been a validated prognostic tool in multiple myeloma (MM) for years but utilization remains limited. We recently developed a novel immunohistochemical (IHC) co-staining technique for CD138 and Ki67 expression to quantify plasma cells in active cycling. Previously presented results from newly diagnosed patients demonstrate that having an elevated ratio of plasma cells in active cycle by co-expression of CD138 and Ki67 (>5%) is associated with aggressive disease and poor outcomes including shorter overall survival (OS). The expansion of subclones with higher proliferative capacity following initial therapy may be an indicator of a higher risk relapse event and indicate poor prognosis. Here we assess MM patients (pts) with Ki67/CD138 co-staining on bone marrow samples both at diagnosis and relapse to assess the impact of changes in cell cycling ratio on outcomes with subsequent therapy and overall clinical course. Methods: A retrospective cohort study of pts with treated symptomatic MM was performed by interrogation of the clinical database at the Weill Cornell Medical College / New York Presbyterian Hospital (WCMC/NYPH). For inclusion in the analysis, pts must have had bone marrow evaluation with double-staining for Ki67 and CD138 by immunohistochemistry both at diagnosis and relapse. Pts must have completed their first line and relapse treatments at WCMC/NYPH. The Ki67% was calculated as the ratio of plasma cells expressing CD138 that were also found to express Ki67. Treatment outcomes were stratified and compared based on alterations in Ki67% between diagnosis and relapse. Results: We identified 37 pts with bone marrow sampling that was evaluated for CD138 and Ki67 co-expression both at diagnosis and at the time of relapse. These pts had undergone a median of 2 lines of prior treatment at the time of relapse bone marrow biopsy (range 1-7). 19 pts were identified to have a rising Ki67% between diagnosis and relapse defined at a 5% or greater increase, the other 18 pts had stable or decreased Ki67%. Pts with a rising Ki67% at relapse had a shorter OS with a median of 72 months vs not reached (p=0.0069), Figure 1. Pts who had rising Ki67% at relapse had shorter progression free survival (PFS) on first line treatment with a median of 25 vs 47 months (p=0.036), Figure 2. Additionally pts with rising Ki67% had a trend towards shorter PFS with the treatment they received after relapse with median of 12.5 vs 3.5 months (p=0.09). Relapse regimens were most commonly carfilzomib (n=9), pomalidomide (5) or ixazomib (4) based. 37% of pts (7/19) with rising Ki67% achieved PR or better on relapsed treatment vs 67% (12/18) with stable Ki67%. Discussion: The presence of clonal evolution and selection of higher risk clones under therapeutic pressure in multiple myeloma is a key feature of disease progression. The ability to improve risk stratification at the time of relapse may help guide clinical decision making to best suit individual patient needs. We have identified rising plasma cell proliferation through quantification of Ki67/CD138 co-expression at relapse to be a useful marker of high risk disease evolution. This appears to help identify the emergence of higher risk clones which are ultimately responsible for treatment resistant disease. Patients with rising Ki67% were more likely than patients with stable Ki67% to have early relapses to initial therapy, were less likely to achieve responses to relapse regimens or to maintain their response and had shorter overall survival. Further evaluation is needed to identify if different approaches to patients with increasing proliferation may improve outcomes in these patients. Figure 1. Figure 1. Figure 2. Figure 2. Disclosures Mark: Calgene: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau. Rossi:Calgene: Speakers Bureau. Pearse:Celegen: Consultancy. Pekle:Celgene: Speakers Bureau; Takeda: Speakers Bureau. Perry:Celgene: Speakers Bureau; Takeda: Speakers Bureau. Coleman:Celgene: Speakers Bureau; Takeda: Speakers Bureau. Niesvizky:Celgene: Consultancy, Speakers Bureau.


Blood ◽  
2009 ◽  
Vol 114 (3) ◽  
pp. 518-521 ◽  
Author(s):  
Prashant Kapoor ◽  
Shaji Kumar ◽  
Rafael Fonseca ◽  
Martha Q. Lacy ◽  
Thomas E. Witzig ◽  
...  

Abstract The outcome of patients with multiple myeloma is dictated primarily by cytogenetic abnormalities and proliferative capacity of plasma cells. We studied the outcome after initial therapy with lenalidomide-dexamethasone among 100 newly diagnosed patients, risk-stratified by genetic abnormalities and plasma cell labeling index. A total of 16% had high-risk multiple myeloma, defined by the presence of hypodiploidy, del(13q) by metaphase cytogenetics, del(17p), IgH translocations [t(4;14), or t(14;16)] or plasma cell labeling index more than or equal to 3%. Response rates were 81% vs 89% in the high-risk and standard-risk groups, respectively. The median progression-free survival was shorter in the high-risk group (18.5 vs 36.5 months, P < .001), but overall survival was comparable. Because of unavailability of all tests for every patient, we separately analyzed 55 stringently classified patients, and the results were similar. In conclusion, high-risk patients achieve less durable responses with lenalidomide-dexamethasone compared with standard-risk patients; no significant differences in overall survival are apparent so far. These results need confirmation in larger, prospectively designed studies.


2014 ◽  
Vol 24 (3) ◽  
pp. 173-181
Author(s):  
E Bolaños ◽  
B Iñigo ◽  
C Benavente ◽  
R Martínez

SummaryMultiple myeloma is a neoplastic proliferation of a plasma cell clone that produces a monoclonal immunoglobulin. It is one of the most common haematological malignancies and the incidence increases with age, with a median age at diagnosis of 65–70 years. The diagnosis of multiple myeloma requires the presence of ≥10% plasma cells in the bone marrow and an M-protein in serum and/or urine. Cytogenetic status, serum β2-microglobulin and response to therapy are the key prognostic factors. Treatment is necessary for the patient diagnosed with symptomatic multiple myeloma, with organ damage. Patients older than 65 years are ineligible for autologous transplantation. The introduction of novel agents, such as thalidomide, bortezomib and lenalidomide, have changed the management of myeloma and extended overall survival. However, in older patients the results are not as satisfactory and treatment strategies have to be individualized to improve tolerability and optimize efficacy.


1991 ◽  
Vol 9 (3) ◽  
pp. 444-448 ◽  
Author(s):  
M Boccadoro ◽  
F Marmont ◽  
M Tribalto ◽  
G Avvisati ◽  
A Andriani ◽  
...  

The efficacy of alternating vincristine, melphalan (M), cyclophosphamide, prednisone/vincristine, carmustine, doxorubicin, and prednisone (VMCP/VBAP) polychemotherapy was compared with the M and prednisone (MP) regimen as induction treatment in multiple myeloma (MM). Three hundred four MM patients entered this study between March 1983 and July 1986; the analysis was performed in December 1989. The treatment groups did not show significant differences with respect to major prognostic factors. Median overall survival was 33.8 months. In the VMCP/VBAP and MP arms, after 12 induction chemotherapy cycles, 59.0% and 47.3% (P less than .068) of the patients achieved an M component reduction greater than 50%. No significant difference was observed in the two treatment arms in terms of remission duration (21.3 v 19.6 months, P less than .66) and survival (31.6 v 37.0 months, P less than .28). Patients younger than 65 years did not show any advantage from the alternating polychemotherapy. At diagnosis, the plasma cell labeling index (LI) and serum beta-2 microglobulin (beta 2-m) were evaluated in 173 and 183 patients, respectively. A significantly reduced survival was observed for patients with LI greater than or equal to 2% (16.4 months) or beta 2-m greater than or equal to 6 mg/L (20.4 months). Even in these poor-risk subgroups, VMCP/VBAP was not superior to MP.


2017 ◽  
Vol 16 (1) ◽  
pp. 142-145
Author(s):  
Bimal K Agrawal ◽  
Anshul Sehgal ◽  
Vikas Deswal ◽  
Prem Singh ◽  
Usha Agrawal

Multiple myeloma is a neoplasm of plasma cells in the bone marrow. It is characterised by lytic lesions in the bones, marrow plasmacytosis and presence of M protein in serum and/or urine. Serum ?2 microglobulin is also raised and can be used for classification and prognostication of the disease. In the absence of M protein, the disease is known as non-secretory myeloma. It is proposed that raised ?2 microglobulin can be used for diagnosis and therapeutic guidance in the absence of M protein. A rare case of nonsecretory myeloma with neurocognitive impairment along with review of literature is being presented. The patient had multiple lytic lesions in bones with marked increase in plasma cells in bone marrow. M protein was not detectable in serum or urine but serum ?2 microglobulin was much elevated.Bangladesh Journal of Medical Science Vol.16(1) 2017 p.142-145


Blood ◽  
2000 ◽  
Vol 96 (4) ◽  
pp. 1505-1511 ◽  
Author(s):  
John Shaughnessy ◽  
Erming Tian ◽  
Jeffrey Sawyer ◽  
Klaus Bumm ◽  
Reid Landes ◽  
...  

Abstract Multiple myeloma (MM) is a hypoproliferative malignancy yielding informative karyotypes in no more than 30% of newly diagnosed cases. Although cytogenetic and molecular deletion of chromosome 13 is associated with poor prognosis, a MM tumor suppressor gene (TSG) has not been identified. To localize a minimal deleted region of chromosome 13, clonotypic plasma cells from 50 consecutive patients with MM were subjected to interphase fluorescence in situ hybridization (FISH) analysis using a panel of 11 probes spanning the entire long arm of chromosome 13. Whereas chromosome 13 abnormalities were absent in plasma cells from 25 normal donors, 86% of patients with MM demonstrated such aberrations. Heterogeneity, both in deletion frequency and extent, was confirmed by simultaneous FISH with 2 chromosome 13 probes. Deletion hot spots were noted at D13S272 (70%) and D13S31 (64%), 2 unlinked loci at 13q14. Homozygous deletions at these loci occurred in 12% (simultaneously in 8%) of the cases. Molecular deletions were found in all 14 patients with morphologic deletions, in 21 of 24 with uninformative karyotypes, and 8 of 12 patients with karyotype abnormalities lacking chromosome 13 deletion. Homozygous deletion of any marker was noted in 4% with low and in 36% with higher plasma cell labeling index greater than 0.4% (P = .01). The absence of increasing deletion incidence and extent with therapy duration suggests that the observed lesions are not induced by treatment. The high incidence and extent of chromosome 13 deletions require the correlation of specific deletion(s) with poor prognosis. These analyses will provide valuable guidance toward cloning of an MM-TSG.


Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 3501-3501
Author(s):  
Jack Jacoub ◽  
Joao L. Ascensao ◽  
Boyer James ◽  
Thomas O’Connor ◽  
Reema Batra ◽  
...  

Abstract Introduction : African-Americans (AA) are twice as likely to develop multiple myeloma (MM) than Caucasians but are largely underrepresented in clinical trials. Thalidmode plus dexamethasone is an established therapy in MM. Biaxin® may augment the efficacy of this combination possibly via potentiating steroid activity (M. Coleman, et al. Leuk Lymphoma 2002, R. Niesvizky, et al. Blood 2003, Abs #832). Methods : We conducted a retrospective review of all AA patients (pts) with symptomatic MM treated with BLT-D from 2002-present. Treatment consisted of Thalidomide 50–200mg daily, Biaxin 500mg twice daily and dexamethasone 40mg weekly. All pts received monthly bisphosphonate therapy and aspirin 81–325mg daily. Response criteria was defined as follows: complete response (CR) = no detectable M-protein, marrow plasma cells &lt;5%; very good partial response (VGPR) = decrease in M-protein by &gt;90%; partial response (PR) = decrease in M-protein by &gt;50%; stable disease (SD) = M-protein decrease by &lt;50% without clinical progression; no response (NR)= progression with no change or increase in M-protein or response &lt;4wks. Progression free survival (PFS) was defined from the start of BLT-D until discontinuation or change in therapy due to progressive disease as clinically indicated. Toxicity was graded according to WHO criteria. Results :15 pts received BLT-D and their characteristics were as follows: all were males; median age 66 (range 30–78); IgG=53%, IgA=20%, light chain only=27%; Durie-Salmon stage I=20%, II=33%, III=47%; International Staging System stage I=20%, II=47%, III=13%, undefined = 20%; 7 were previously treated (5 pts had 1 prior regimen, 2 pts had ≥2 prior regimens). In previously treated pts (n=7) responses were as follows: no CR, 2 VGPR (28%), 3 PR (43%), 1 SD (14%) and 1 NR (14%) for an overall response rate (ORR) of 87%. Their duration of treatment ranged from 4–32 mos and median PFS in responders (VGPR+PR+SD) was 29.5 mos (range 23–35). 3 pts had BLT-D discontinued after 12–15 months of therapy and remained in stable plateau phase off therapy for &gt; 1 year; one was referred for ASCT after 14 mo; one continues stable at 15 mo and the third relapsed at 12 months but failed to respond again to BLT-D. Responses in treatment naive pts (n=8) were as follows: no CR, 3 VGPR (38%), 1 PR (13%) and 2 SD (25%), 2 NR (25%) for an ORR of 75%. Their duration of therapy ranged from 3–20 mos and median PFS in responding patients was 11 mos (range 7–20). The longest survivor in this group (37 mos) received an ASCT after 12 mos of therapy. 13 pts (87%) remain alive at a median follow-up of 24 mos (range 8–37). Grade 3–4 toxicity consisted of 3 DVTs + 1 PE (27%), 5 hypergycemias (33%), 2 infections (13%) and 1 peripheral neuropathy (7%). Additionally, 1 pt developed superficial thrombophlebitis; 1 QT prolongation resolving with Biaxin discontinuation; 5 others with neuropathy; and 2 others with hyperglycemia. Conclusion : BLT-D is feasible and effective therapy in African-American patients with MM and is capable of inducing durable responses. However, we encountered significant thrombotic and endocrine toxicity that appears out of proportion to what has been previously reported with thalidomide plus dexamethasone alone. Furthermore, aspirin thromboprophylaxis at daily doses of 81–325 mg appears suboptimal in preventing thromboembolic events in this group of patients when prescribed this regimen.


Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 5080-5080 ◽  
Author(s):  
David Dingli ◽  
Robert A. Kyle ◽  
Vincent S. Rajkumar ◽  
Grzegorz S. Nowakowski ◽  
Dirk R. Larson ◽  
...  

Abstract Background: Solitary plasmacytoma of bone (SBP) is a localized collection of monoclonal plasma cells that is potentially curable with local radiation therapy but associated with a high risk of progression to multiple myeloma. We hypothesized that an abnormal immunoglobulin free light (FLC) ratio at diagnosis may be a prognostic indicator of transformation risk. Methods: We identified a cohort of 133 patients with SBP for whom stored serum taken at the time of diagnosis was available. The diagnosis was ascertained and serum FLC determined in 126 patients. Results: From this cohort, 48 patients have progressed to myeloma and the median time to progression among those who progressed was 1.9 years. On univariate analysis, age (p&lt;0.001), gender (p=0.035), abnormal FLC ratio at diagnosis (p=0.009) and persistence of serum or urine M-protein after therapy (p=0.0070 were all associated with a shorter overall survival (OS) and time to progression to multiple myeloma. Progression by Normal FLC(0.26–1.65) Progression by Normal FLC(0.26–1.65) On multivariate analysis, an abnormal FLC ratio retained its independence in a model that includes age at diagnosis but lost its significance when combined with persistence of the serum or urine M-protein. However, serum or urine M-proteins are not detectable in a significant number of patients with SBP and therefore not informative. Conclusion: The FLC ratio at the time of diagnosis of SBP is a powerful predictor of risk and a useful aid to management of patients with this condition.


Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 2728-2728
Author(s):  
Vrushali s Dabak ◽  
Esther Urbaez Duran ◽  
Muath Dawod ◽  
Amr Hanbali

Abstract Introduction: Monoclonal gammopathy of undetermined significance (MGUS) is defined as the presence of a serum monoclonal protein &lt;3g/dl, with fewer than 10% plasma cells in bone marrow and absence of lytic bone lesions, anemia, hypercalcemia and renal insufficiency. Incidence increases with age, especially over 70 and its progression to malignant disease occurs at 1% per year. However, so far there are no studies which can reliably distinguish patients who would progress from those who would remain stable. Based on available literature, it is concluded that MGUS has low risk of progression when M-protein is less than 1.5 g/dl, with no reduction in polyclonal immunoglobulins and bone marrow plasma cells less than 5%. The recommended testing with suspected MGUS is hemoglobin concentration, protein studies, serum calcium, and creatinine. Metastatic bone survey (MBS) and bone marrow aspiration are felt unnecessary if M-protein is less than 1.5 g/dl. However literature to support the use of MBS at diagnosis based on the level of M-protein is limited. Also our observation has been that due to lack of clear guidelines, most physicians obtain a baseline MBS and some follow patients with yearly or every other year MBS irrespective of the level of M-protein. Hence, we decided to review patients diagnosed with MGUS at our institution to determine the importance of MBS and if possible identify risk factors like age, race, M-protein level, hemoglobin concentration, serum calcium or creatinine level, which would identify a subgroup of patients needing a MBS. In doing so we were hoping to separate out those patients in whom we could recommend against unnecessary use of the skeletal survey below a certain defined M protein level. Study: We reviewed charts on 1906 patients at Henry Ford hospital diagnosed with MGUS between 1990 and 2007. All patients with at least one M-protein and one MBS done were included in the analysis. We excluded patients with a level of M-protein &gt;3.0 g/dl, who never had a skeletal survey in our system, had a light chain myeloma, plasmacytoma, chronic lymphocytic lymphoma(CLL), amyloidosis or protein evaluation done for diagnosis other than MGUS. We had 620 such patients. We collected data regarding their age, sex, ethnicity, date of diagnosis, type and level of the M-protein, hemoglobin level, serum calcium and creatinine at baseline, result of the MBS, date of progression to multiple myeloma (MM) if any and the date of last follow up if they did not progress to MM. Positive MBS is defined as x ray findings consistent with myelomatous changes with bone marrow aspiration confirming diagnosis of MM. Results: Of 620 patients, 36 had a positive MBS and applying non parametric Mann Whitney test and a chi-squared test, positive results seemed to correlate with higher level of M-protein, IgG subtype, lower hemoglobin and higher creatinine. Male sex and older age were other risk factors. Using the LOES curve to graph the risk of a positive skeletal event with the level of M-protein, risk was noted to increase significantly with M-protein in the range of 1.8– 3.0 (odds ratio 8.84 compared with 1.31 if level was less than 1.8), which was highly statistically significant as shown in figure 1. Further for 97/620 who progressed to multiple myeloma, the risk of progression was significantly higher for males, younger age at diagnosis of MGUS, lower hemoglobin, higher level of M-protein, IgG subtype and a positive skeletal event. Discussion: Our study is a retrospective chart review with its own limitations. However to our knowledge this is the first study to define the level of M-protein in patients with MGUS above which obtaining a MBS may be of value. Our study identifies 1.8 as a cut off value of M-protein below which doing routine MBS without symptoms of bone pains or other laboratory features suggesting progression to multiple myeloma might be unnecessary. Other risk factors for a positive event and progression to MM like lower hemoglobin, higher creatinine, older age, male sex and IgG subtype in our study are in keeping with what has been described in the literature. Conclusion: Based on our study, obtaining baseline MBS in all patients with suspected MGUS was not beneficial. Hence, we would not recommend obtaining MBS in patients with M-protein &lt;1.8 g/dl in absence of other risk factors for progression to multiple myeloma. Figure 1: LOES curve showing increased likelihood of positive MBS for increasing MPEV level. Figure 1:. LOES curve showing increased likelihood of positive MBS for increasing MPEV level.


Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 5176-5176 ◽  
Author(s):  
Andrzej J. Jakubowiak ◽  
Malathi Hari ◽  
Tara Kendall ◽  
Yasser Khaled ◽  
Shin Mineishi ◽  
...  

Abstract It has been proposed that treatment failures in multiple myeloma (MM) are related to the chemoresistance of a subset of malignant myeloma cells with clonogenic potential to the anti-myeloma drugs (Matsui et al., Cancer Research2008, 68:190). Studies suggest that these putative myeloma stem cells (MSC) are CD138neg and express CD20, which is usually absent in more differentiated malignant plasma cells (Matsui et al., Blood2004, 15:2332). These findings provided a rationale for a treatment strategy to eliminate chemoresistant clonogenic MSC using anti-CD20 antibodies. To evaluate the clinical effects of anti-CD20 treatment, we developed a phase II trial with Bexxar as a consolidation treatment for MM. We hypothesized that Bexxar would be more efficacious than unlabeled antibody in the eradication of highly radiosensitive myeloma cells by both direct and cross-fire effects. Preclinical studies showed that tositumomab, the antibody used in Bexxar, inhibited colony formation of clonogenic myeloma cells. To be eligible for Bexxar treatment, patients must have completed at least 4 cycles of therapy (1st to 3rd line) and have measurable disease in a plateau of at least partial response (PR). To date, 10 of 30 patients have been enrolled, of which 5 were treated with Bexxar after completion of initial therapy prior to proceeding to autologous stem cell transplant (ASCT). Patients proceeding to ASCT required hematopoietic stem cells collection prior to Bexxar and 3 months after Bexxar. Eight patients are evaluable for response and toxicities. At 3 months post Bexxar, 1 patient achieved a partial response (PR), 4 patients had stable disease (SD), and 1 patient progressed (PD). At 1 year post Bexxar, 1 patient with initial PR achieved CR and remains in CR, 1 patient is in unconfirmed CR, 2 are in partial response (PR), and 3 remain in SD. After a median 20 months of followup (range 4–24), all patient are alive, 4 in continued response, 3 with SD. Hematological toxicities were mild to moderate (1 patient grade 3 and 4 patients grade 2 thrombocytopenia, 4 patients grade 2 neutropenia). Non-hematological toxicity was limited to HAMA (6 patients). Out of patients who received Bexxar prior to transplant, 3 collected stem cells post-Bexxar without problems, one requires re-collection. Three patients who proceeded to ASCT to date using the post-Bexxar stem cell collection, engrafted at 11–12 days, and had no unexpected toxicities with ASCT. We also analyzed CD20+ cells in bone marrow aspirates (BM) and stem cell collections (SCC) using samples collected from 4 patients before and after Bexxar. Bexxar treatment eliminated a median 80% of CD20+ cells (range 23–97). For a given patient, elimination of CD20+ cells from SCC correlated with elimination of CD20+ cells from BM. The most complete elimination of CD20+ cells from BM was observed in 2 patients who at 1 year achieved CR (94% and 97%), compared to patients who achieved PR (23% and 68%). We conclude that anti-CD20 consolidation treatment of myeloma patients with Bexxar used as targeted therapy against clonogenic myeloma cells is feasible and well tolerated. Clinical outcomes to date are encouraging considering that clonogenic MSC represent &lt;5% of malignant plasma cells and delayed responses observed in this study could be expected. While early, clinical outcomes appear to correlate with the efficacy of the CD20+ cell elimination by Bexxar treatment in myeloma.


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