Citations 999

Deletion 13 by FISH Provides Prognostic Information on Overall Survival and Time to Progression Independent of Serum Beta 2 Microglobulin and Bone Marrow Plasma Cell Labeling Index in Myeloma Patients Undergoing Stem Cell Transplantation.

Blood | April 18, 2020 | Volume: 104 | Issue: 11 | Pages: 4852-4852

10.1182/blood.v104.11.4852.4852

Abstract INTRODUCTION The bone marrow plasma cell labeling index (PCLI) and the beta 2 microglobulin (β2M) when combined provide a powerful staging system highly predictive of outcomes in myeloma patients (Greipp et. al., Blood, 81:3382–87, 1993). This staging system lacks information on cytogenetics and it has been demonstrated that deletion 13 (Δ13) by conventional cytogenetics is associated with poor outcomes. In conventionally treated patients Δ13 by FISH is an independent prognostic variable. We analyzed the importance of Δ13 by FISH in a cohort of patients receiving high dose therapy and assessed its value relative to known prognostic parameters, PCLI and β2M. PATIENTS AND METHODS 238 patients undergoing high dose therapy between January 1990 and September 2001 were studied. The minimum follow-up of patients was 34 months. The median age of the cohort 56 years. Interphase fluorescence in situ hybridization with Probes LSI13/D13S319 was performed with simultaneous immunofluorescent detection of bone marrow plasma cells by the presence of cytoplasmic immunoglobulin. PCLI was done by a slide-based immunofluorescence method with antibodies to bromodeoxyuridine. RESULTS Of the 238 patients studied 215 had a successful FISH analysis and 212 of these had a bone marrow labeling index. Deletion 13 was absent in 104 patients (48%) and present in 111 patients. The overall survival and time to progression for patients lacking and having deletion 13 was 47.8 vs 26.4 (OS) and 19.0 vs 11.7 (TTP)months respectively. A Cox model was constructed with the PCLI, the presence or absence of deletion 13 and serum β2M. Although all three variables were independently predictive of survival and time to progression, the β2M was the weakest of these three variables. The hazard function for survival for PCLI, deletion 13 and β2M was 1.4, 1.6 and 1.1 respectively. A staging system was constructed assigning 1 point for the presence of deletion 13 or a PCLI ≥ 1%. Patients fell into 3 categories of 0 points (N=69), 1 point (N=104) and 2 points (N=39). The overall survival for the three groups respectively were 56.5, 36.6 and 13.7 months (figure). The time to progression for the three groups were 22.3, 15.4 and 8 months (P<0.001). When analysis was limited to those patients transplanted within 12 months of diagnosis the results remained significant (P<0.003) with median survivals of stage 0, 1 and 2 of 72.5, 59.1 and 15.4 months respectively. TTP for stage 0, 1 & 2 in this same cohort of patients transplanted < 12 mos after diagnosis is 30.6, 21.5 & 8.2 months respectively. CONCLUSION Deletion 13 by FISH is an independent predictor of survival and time to progression providing information independent of the β2M and the PCLI. Combining the PCLI with FISH del 13 identifies patients who following transplant have a median time to progression of 8 months and a median OS of 13.7 months. This group may not benefit from autologous transplant and are candidates for novel therapeutic approaches. Figure Figure
Activation of MYC Pathway Is a Unifying Pathological Event in the Progression from Monoclonal Gammopathy of Undetermined Significance (MGUS) to Myeloma (MM).

Blood | April 18, 2020 | Volume: 110 | Issue: 11 | Pages: 241-241

10.1182/blood.v110.11.241.241

Abstract Events mediating transformation from the pre-malignant MGUS to MM is largely unknown. Previous studies have highlighted RAS mutation as a progression event. However, this abnormality is present in only a small subset of patients. Global gene expression differences between MGUS and MM have been reported but provided little coherent biological insights. To define progression events, we examined the differences in gene expression profiles (GEP, Affymetrix U133A genechip) between 101 MM and 22 MGUS using a powerful functional genomic tool, Gene Set Enrichment Analysis (Subramanium et al PNAS 2005), that allow extraction of biological information based on enrichment of genes associated with a phenotype within gene-sets derived experimentally or extracted from database. We found that a predominant theme relating to MM progression is the over-expression of proliferation related genes in MM highlighted by the enrichment of cell cycle related gene-sets. Another common theme is the enrichment of gene-sets relating to MYC activation. Seven of eight gene-sets related to MYC activation in the database are significantly enriched (p-value <0.05 and false detection rate <0.05). Leading edge (enriched genes) analysis of enriched MYC-related and proliferation-related gene-sets revealed a core, overlapping signature of 8 genes specific to MYC and not proliferation. These genes are further verified as MYC transcriptional targets using Metacore, a network analysis tool. In addition, 7 of the 8 genes had been validated as MYC target genes by chromatin immunoprecipitation previously (www.myccancergene.org). We validated this signature in independent publicly available cell lines and mouse gene expression experiments where this signature is present in mammary epithelial cell lines engineered to over-express MYC but not E2F3, SRC and BCAT, and mouse embryonic fibroblast over-expressing MYC but not HER2 or with RB knocked-out. In addition, analysis of proliferation index in these datasets showed that there is dissociation of proliferation from this signature. This showed conclusively that our signature is MYC specific and not related to proliferation. Of interest, the signature is also present in cell lines with activating RAS mutation, which also have high expression of MYC, suggesting that MYC activation is a downstream effect of activated RAS signaling. Indeed, in our patient cohort, most patients with RAS mutation express this signature. When applied to 2 large GEP MM patient cohorts, this signature was not present in normal plasma cells, rarely present in MGUS, and present in a significant proportion of MM and almost all the human myeloma cell lines. When analyzed in the context of other B-cell malignancies, the signature is very strong in Burkitt’s lymphoma, present in most myeloma but absent in chronic lymphocytic leukemia, Waldenstrom Macroglobulinemia, and normal B-cells. Our analysis therefore suggests that MYC activation may be a unifying pathological event in MGUS to MM progression. As MYC translocations occur in only about 13% of newly diagnosed MM patients, activating RAS mutations and other trans-mechanisms may mediate MYC activation. Our recent demonstration that sporadic MYC activation in a mouse strain prone to monoclonal gammopathy led to MM development provides important functional proof.
Low Dose Single Agent Thalidomide Is Tolerated in Patients with Primary Systemic Amyloidosis, but Responses Are Limited.

Blood | April 18, 2020 | Volume: 104 | Issue: 11 | Pages: 4920-4920

10.1182/blood.v104.11.4920.4920

Abstract Background: Primary systemic amyloidosis (AL) is an incurable plasma cell dyscrasia with limited therapeutic options. Based on the observed 25 to 50% partial response rates in myeloma patients, thalidomide has been tried in patients with AL. Two reports (Dispenzieri et al, Amyloid10:247; 2003; Seldin et al, Clinical Lymphoma3:241; 2003) have demonstrated that standard dose, single agent thalidomide (≥ 200 mg per day) has a higher than expected rate of adverse events in AL patients without hematologic or organ response, potentially due to rapid patient attrition. We therefore performed a prospective clinical trial using low dose, single agent thalidomide in patients with AL. Methods: In August 2001, we began accrual to a phase II trial of low dose thalidomide for patients with AL. Eligibility included: age ≥ 18 years, creatinine <3mg/dL, total bilirubin < 3 mg/dL, ANC ≥ 1 x 10(9)/L, left ventricular ejection fraction of >45%, histochemical proof of amyloid and a monoclonal plasma cell dyscrasia, symptomatic organ involvement, and ability to supply informed consent. Patients were started with thalidomide 50 mg per day, with a dose escalation to a maximum dose of 400 mg per day over a 19 week period as tolerated. Patients were evaluated monthly by their physician. These office visits were staggered with telephone toxicity checks monthly by the primary investigator. The endpoint of the study was hematologic and organ response by 12 months. Results: Eighteen patients were treated. The median age was 66 years (range 43–83). Eight were male. Twenty-eight percent had an ECOG performance status of 2 or 3. Five patients (28%) had received no prior therapy. Five had received one prior regimen; 6, two prior; and 2, ≥ three. Three had received prior PBSCT. Sixteen patients had a monoclonal lambda plasma cell disorder; two, monoclonal kappa. Immunoglobulin heavy chains were IgG (n=9), IgM (n=5), IgA (n=1), and none (n=3). Twelve patients (67%) had cardiac involvement; twelve (67%) renal; two liver; two symptomatic gastrointestinal; one pulmonary; and two nerve involvement. Study participants had significant symptomatology at baseline with dyspnea (n=12), light-headedness (n=6), and edema (n=13). Median number of organs involved was 1, range (1 to 4). Median time on study drug was 5.6 months, range 0.7–24 months. Reasons for discontinuation included: progression, 7 (39%); 3 each (17%) for adverse events, death, and patient refusal; and other causes in 2. The median tolerated dose was 100 mg. There were no hematologic responses observed. The overall organ response rate was 11%. There was one renal response at 1 year and a gastrointestinal response at 3 months with 24 hour fecal fat changing from 21 to 8.7 grams. The most common adverse effects attributable to thalidomide were: constipation (78%), edema (44%), sinus bradycardia (17%), dyspnea (11%), and paresthesias (11%). Light-headedness, rising creatinine, thrombosis, infection, syncope, and rash was attributed to the thalidomide in 5.6% of patients. Conclusions: Low dose thalidomide is tolerable in this fragile group of patients, but as a single agent efficacy is limited. Further study of combination therapy of thalidomide and low dose dexamethasone may be warranted. A study using the next generation immune modulatory drug Revlimid is scheduled to open to accrual. Funded by NIH grant CA 91561 and Celgene.
Time Interval from Last Chemotherapy to Stem Cell Collection Correlates with Peripheral Blood Absolute Lymphocyte Count at Apheresis and Survival Post-Autologous Stem Cell Transplantation in Non-Hodgkin’s Lymphoma.

Blood | April 18, 2020 | Volume: 104 | Issue: 11 | Pages: 2927-2927

10.1182/blood.v104.11.2927.2927

Abstract The infused autograft absolute lymphocyte count (A-ALC) is an independent prognostic factor for survival after autologous hematopoietic stem cell transplant (AHSCT) in non-Hodgkin’s lymphoma (NHL). Previous studies have shown that A-ALC directly correlates with the peripheral blood absolute lymphocyte count (PC-ALC) at the time of apheresis collection. However, factors affecting the PC-ALC at apheresis remain undefined. We hypothesized that one possible factor impacting PC-ALC may be the time interval from last chemotherapy to stem cell collection (TILC). Data from 160 patients who underwent AHSCT for treatment of relapsed NHL at Mayo Clinic between 1993 and 2001 were collected and analyzed. The primary end point of this study was correlation between TILC and PC-ALC, and our analysis revealed a strong correlation (r = 0.67, p < 0.0001). Further analysis revealed higher PC-ALC numbers in patients with TILC ≥ 60 days versus TILC < 60 days (median of 7.44 x 109/L in the ≥ 60 day group versus 3.87 x 109/L in the < 60 day group, p < 0.0001). Both the median overall survival (figure below) and the progression-free survival were longer in the TILC ≥ 60 days group versus the TILC < 60 days group (76 versus 21 months, p < 0.0037; 76 versus 11 months, p < 0.018, respectively). These findings were independent of other prognostic indicators for relapsed NHL patients undergoing APHSCT. The data supports our hypothesis that TILC affects PC-ALC and survival post-AHSCT in NHL. Figure Figure
Oncolytic Measles Virus Selectively Targets CD46 Overexpression on Myeloma Cells.

Blood | April 18, 2020 | Volume: 104 | Issue: 11 | Pages: 2392-2392

10.1182/blood.v104.11.2392.2392

Abstract Multiple myeloma remains incurable and novel therapeutics are urgently needed. We have shown that live attenuated Edmonston strain measles virus (MV-Edm) is potently oncolytic in multiple myeloma xenograft models and can efficiently infect CD138 sorted primary myeloma cells inducing extensive intercellular fusion which leads to cell death (Blood, 2001, v98, p2002). In contrast, the virus causes minimal damage to normal PHA-stimulated peripheral blood lymphocytes, fibroblasts and smooth muscle cells. To facilitate non-invasive imaging of sites of viral gene expression, we introduced the human thyroidal sodium iodide symporter (NIS) gene into the viral genome (MV-NIS). MV-NIS infected myeloma cells efficiently concentrate radioiodine which provides a basis for noninvasive imaging and destruction of infected tumors using beta emitters such as 131I (Blood, 2004, v103, p1641). Clinical translation of MV-NIS in patients with refractory myeloma is planned. However, the mechanism underlying the tumor selectivity of MV-Edm has not previously been defined. MV-Edm uses either of two cellular receptors for cell entry and cell fusion; CD46, a regulator of complement activation, is expressed on all nucleated cells, wheras SLAM (signaling lymphocyte activation molecule) is expressed only on activated B lymphocytes, T lymphocytes, and monocytes, and is not present on myeloma plasma cells. Using a panel of CHO cell transfectants, we demonstrated that MV-Edm -mediated cell killing increases exponentially above a threshold CD46 receptor density (Can Res, 2004, v64, p4919). We subsequently obtained bone marrow aspirates from 18 myeloma patients and performed multi-parameter flow cytometry to determine the relative expression levels of CD46 on the myeloma plasma cells versus the rest of the hematopoietic cells in the bone marrow. The myeloma cells expressed significantly higher levels (5-fold) of CD46 receptors (MFI=294.9 + 204.4, means ± SD) on their cell surfaces compared to hematopoietic cells of the erythroid, myeloid and lymphoid lineages (MFI=58.6 ± 9.0). Analysis of the myeloma array data generated by the Shaughnessy lab indicated that, in comparison to plasma cells from healthy volunteers (2997 ± 1053, n=30, means ± SD), primary myeloma cells express 2-fold elevated levels of CD46 mRNA (6592 ± 4029, n=72, p=0.001, Wilcoxon signed rank test). Taken together, these findings provide strong support for the hypothesis that selective destruction of myeloma cells by oncolytic measles viruses is a direct consequence of their overexpression of the cellular receptor CD46.
Interleukin-1 Receptor Antagonist (IL-1Ra) Targets the Proliferative Component in Early Stage Myeloma.

Blood | April 18, 2020 | Volume: 104 | Issue: 11 | Pages: 2412-2412

10.1182/blood.v104.11.2412.2412

Abstract Background: It has been hypothesized that multiple myeloma (MM) remains incurable due to a stemcell/proliferative component that responds only partially to standard treatment regimens. We have shown that abnormal production of IL-1beta in the myeloma microenvironment stimulates the generation of paracrine IL-6, the central myeloma growth factor, and that IL-1Ra will inhibit paracrine IL-6 production in vitro. Based on these preclinical studies, we have developed a Phase II trial using IL-1Ra. Purpose: To determine the biologic and clinical activity of IL-1Ra (Anakinra) in a subgroup of smoldering MM (SMM) patients that present with an elevated plasma cell labeling index (PCLI; a measure of myeloma cell proliferation). Methods: 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. Patients received 100 mg of Anakinra (IL-1Ra) SQ qd for a total duration of 6 months. Results: Eleven of 29 patients enrolled on the protocol had an on-study PCLI > 0 and have completed six months of therapy with IL-1Ra. Seven of the 11 patients had a decrease in the PCLI of 75–100% (see Table), three had only modest changes (≤ 50%), and one had an increase. The decrease in the PCLI paralleled a decrease in the high sensitivity C-reactive protein (CRP) in all cases (43–90% decrease). The above results suggested that IL-1Ra inhibited IL-6 production in the myeloma microenvironment, as evidenced by a reduction in the CRP, resulting in suppression of myeloma cell growth. However, there was little effect on the M-protein. To investigate these clinical observations, we co-cultured IL-1beta transduced +/− myeloma cells with stromal cells +/− dexamethasone (DEX), IL-1Ra, or both for 48 hours and quantitated the percent apoptotic cells by flow cytometry and IL-6 production by ELISA. The results showed: 1) IL-1Ra was superior at inhibition of IL-6 but caused no increase in apoptosis; 2) the DEX apoptotic effect was eliminated by IL-6 3) DEX and IL-1Ra combined induced maximal IL-6 inhibition and apoptosis of myeloma cells. Based on these in vitro results, 5 of the 11 patients have been advanced to IL-1Ra + low dose DEX (20 mg/week) resulting in 4/5 minor responses (25–50% decrease M-spike) and 1/5 with stable disease. Conclusion: The use of IL-1Ra is a novel targeted therapeutic strategy that interferes with myeloma cell growth. By inhibiting IL-1beta induced IL-6 production, IL-1Ra specifically targets the proliferative myeloma fraction and also complements DEX induced apoptosis. Preliminary studies on the use of IL-1 inhibitors in SMM patients to delay/prevent progression to active MM and to minimize toxicity appear encouraging, however, more patients need to be studied. Patient # On Study 6 months % Change 1 PCLI 0.8% 0% −100% CRP (mg/L) 2.01 0.58 − 71% M-spike (g/dL) 2.5 2.4 − 4% 2 PCLI 0.2% 0% − 100% CRP 0.89 0.51 − 43% M-spike 2.8 2.7 − 3% 3 PCLI 0.2% 0% − 100% CRP 5.7 1.02 − 82% M-spike 2.9 2.9 0% 4 PCLI 4.1% 1% − 75% CRP 3.39 1.51 − 55% M-spike 3.8 3.6 − 5% 5 PCLI 0.4% 0% − 100% CRP 3.46 0.34 − 90% M-spike 2.7 3.1 15% 6 PCLI 0.3% 0% − 100% CRP 17 5.35 − 68% M-spike 4.4 3.9 − 11% 7 PCLI 1.2% 0% − 100% CRP 1.06 0.32 − 70% M-spike 3.1 2.9 − 6%
Immunoglobulin light chain amyloidosis: 2020 update on diagnosis, prognosis, and treatment

American Journal of Hematology | April 8, 2020 | Volume: 95 | Issue: 7 | Pages: 848-860

10.1002/ajh.25819 | PMID 32267020

Abstract Disease Overview Immunoglobulin light chain amyloidosis is a clonal, nonproliferative plasma cell disorder in which fragments of immunoglobulin light or heavy chain are deposited in tissues. Clinical features depend on organs involved but can include heart failure with preserved ejection fraction, nephrotic syndrome, hepatic dysfunction, peripheral/autonomic neuropathy, and “atypical smoldering multiple myeloma or monoclonal gammopathy undetermined significance (MGUS).” Diagnosis Tissue biopsy stained with Congo red demonstrating amyloid deposits with apple‐green birefringence is required for diagnosis. Invasive organ biopsy is not required in 85% of patients. Verification that amyloid is composed of immunoglobulin light chains is mandatory. The gold standard is laser capture mass spectroscopy. Prognosis N‐terminal pro‐brain natriuretic peptide (NT‐proBNP), serum troponin T, and difference between involved and uninvolved immunoglobulin free light chain (FLC) values are used to classify patients into four groups of similar size; median survivals are 94.1, 40.3, 14.0, and 5.8 months. Therapy All patients with a systemic amyloid syndrome require therapy to prevent deposition of amyloid in other organs and prevent progressive organ failure. Stem cell transplant (SCT) is preferred, but only 20% of patients are eligible. Requirements for safe SCT include systolic blood pressure >90 mmHg, troponin T < 0.06 ng/mL and serum creatinine ≤1.7 mg/dL. Nontransplant candidates can be offered cyclophosphamide‐bortezomib‐dexamethasone or daratumumab‐containing regimens as it appears to be highly active in AL amyloidosis. Future Challenges Delayed diagnosis remains a major obstacle to initiating effective therapy prior to the development of end‐stage organ failure.
Clinical and cytogenetic features of nonsecretory multiple myeloma (NSMM) in the era of novel agent induction therapy: The Mayo Clinic experience.

Journal of Clinical Oncology | March 12, 2020 | Volume: 37 | Issue: 15_suppl | Pages: e19519-e19519

10.1200/jco.2019.37.15_suppl.e19519

e19519 Background: NSMM is a rare subtype of myeloma that has not been well characterized in the era of novel agent induction therapy. Thus, we evaluated the clinical and cytogenetic features of patients with newly diagnosed NSMM evaluated at our institution. Methods: We evaluated all NSMM patients seen at the Mayo Clinic, Rochester from 2008-2017 based on the absence of a detectable monoclonal protein in their serum and urine electrophoresis and having a concurrent involved serum immunoglobulin light chain of less than 5 mg/dL. Survival analysis was performed by the Kaplan-Meier method and clinical and cytogenetic features were reported descriptively. Results: This cohort consisted of 30 consecutive patients with NSMM with a median age of 62 years (40-79) of which 16 (53%) were male. The median bone marrow plasma cell involvement was 70% (Range: 0 – 100). There were 3/25 (12%) patients who presented with a creatinine of 2 mg/dL or greater and 6/23 (26%) patients who presented with hypercalcemia (11 mg/dL or greater). The ISS classification of this cohort is as follows: Stage 1- 8 (36%) patients, Stage 2- 3 (14%) patients and Stage 3- 11 (50%) patients. There were 6 (21%) out of 28 patients with high risk cytogenetics (either del 17p, t(4;14), t(14;16) or t(14;20). The distribution of primary cytogenetic abnormalities among this cohort was as follows: t(11;14) – 16 (57%), t(4;14) – 1 (4%), trisomies – 6 (21%) and other - 5 (13%). The median overall survival (OS) for patients in this cohort was 59 months (95% CI: 34 – 64). In comparison to a control cohort of newly diagnosed secretory myeloma patients matched for age, gender and year of diagnosis in a 1:2 ratio, the median OS was worse for the NSMM cohort but this was not statistically significant (59 vs. 92 months, p = 0.257). Conclusions: Patients diagnosed with NSMM had a predisposition towards having a t(11;14) primary cytogenetic abnormality. In the era of novel agent induction therapy, they may have a survival outcome that may be worse than newly diagnosed secretory myeloma patients.
Continued improvement in survival in multiple myeloma (MM) including high-risk patients.

Journal of Clinical Oncology | March 12, 2020 | Volume: 37 | Issue: 15_suppl | Pages: 8039-8039

10.1200/jco.2019.37.15_suppl.8039

8039 Background: Treatment of MM has evolved significantly over the past decade, with increasing use of multi-drug combinations for initial therapy. In addition, supportive care approaches have also improved. We examined how these improvements have translated to survival outcomes in patients with newly diagnosed MM. Methods: Patients (n=3449) with a diagnosis of MM made between 2004 and 2017 and seen at Mayo Clinic within six months of the diagnosis, were included in this analysis. Patients were divided into three groups based on the year of diagnosis; group 1- 2004-07 (n=831), group 2-2008-12 (n=1161), and group 3-2013-17 (n=1457). Survival of the groups were estimated using Kaplan-Meier method, and compared using log rank test. Results: The median age was 64 years (22 to 96); 60% were male and 40% were female. 14% were >75 years, 33% were aged 65-75 and 53% were <65 years. The median overall survival for the whole cohort was 5.7 years (95%CI; 5.4, 6.3). The median OS for the groups 1, 2 and 3 were 3.9, 6.3 and NR, respectively; p<0.001. The 4-year survival estimates were 50%, 62%, and 75%, respectively. We then explored the improvements in patient subgroups. While all patients experienced improvements in OS over time, improvement in group 3 was most prominent for those >75 years. In patients <65 years, the 4-yr OS for groups 1, 2 and 3 were 57, 71, and 79% respectively. In patients 65-75 years of age, the 4-yr OS for groups 1, 2 and 3 were 48, 60, and 75% respectively. In patients >75 years, the 4-yr OS for groups 1, 2 and 3 were 24, 35, and 56% respectively. While patients with high-risk disease did not see as much benefit in the earlier period, substantial progress was seen in the last group. The 3-yr OS for patients with high-risk cytogenetics were 52, 55, and 73% for groups 1, 2 and 3 compared to 67, 75, and 85% for standard-risk cytogenetics respectively. 2067 patients were staged according to the International Staging System and the median OS for stages 1, 2 and 3 were 6.5, 4.6 and 2.4 in group 1; 9.2, 6.6 and 3.5 in group 2 and NR for any of the stages in group 3. Conclusions: The results confirm continued improvement in survival of newly diagnosed multiple myeloma patients, including elderly and high-risk MM.
Implications and outcomes of MRD-negative multiple myeloma patients with immunofixation positivity.

Journal of Clinical Oncology | March 12, 2020 | Volume: 37 | Issue: 15_suppl | Pages: 8034-8034

10.1200/jco.2019.37.15_suppl.8034

8034 Background: Minimal residual disease (MRD) assessment in multiple myeloma (MM) has improved our ability to assess disease activity, resulting in more advanced prognostication. While MRD assessment remains confined to the bone marrow (BM) plasma cell population, serum studies including immunofixation (IFE) are required to complete response evaluation. The significance of those who are MRDneg yet have detectable monoclonal protein through IFE remains unclear. Methods: We retrospectively studied 256 MM patients who had MRD assessment via the Euroflow multiparametric flow cytometry on the BM with concomitant serum IFE testing. Patients who were MRDneg were included in the study. Outcomes included probability of disease progression (PD) at 1 year. The Cox-proportional hazards model was used to compare probability of PD among different groups. Time to progression (TTP) was calculated as the difference from date of MFC analysis to PD in months. Results: Among the entire cohort, 178 (70%) patients were MRDneg and median follow-up from MRD assessment was 6.3 months. Among these patients, 74 (42%) had a positive IFE at the time of MRD analysis. Within the MRDneg/IFEpos group, 31 (42%) patients remained IFEpos after a median follow up of 5.5 mo from initial MRD/IFE testing while 34 patients eventually became IFEneg after a median of 2.8 mo with no subsequent IFE available in 9 patients. The 1 year probability of PD in the MRDneg/IFEneg group was 20% compared to 41% in the MRDneg/IFEpos group (P < 0.01, Wilcoxon test). When comparing subsequent IFE status in those who were MRDneg/IFEpos, those who remained IFEpos had a trend towards shorter TTP compared to patients who later became IFEneg. Conclusions: Persistent monoclonal protein in the face of MRD negativity predicts for a shorter TTP. This likely reflects persistent disease that was not sampled on the BM aspirate in many of these patients compared to those who eventually become IFEneg with a trend towards longer TTP owing to the prolonged half-life and therefore clearance of M protein. This supports the current strategy of assessing for MRD at the time of suspected complete response to reduce the chance of positive MRD tests and thus avoidance of multiple BM exams.