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Abstract The use of soluble cardiac biomarkers such as NT-proBNP and troponin has revolutionized prognostication for patients with AL amyloidosis and led to their use in the Mayo 2004 and 2012 staging systems. Novel soluble markers with different phenotypic targets may further improve this approach. Soluble ST2 (sST2), which is the circulating form of the IL-33 receptor, has been shown to be a marker of cardiac remodelling and fibrosis, is predictive of mortality in patients with congestive heart failure, and is predictive of risk of GVHD and GVHD mortality. Samples of blood of patients with AL amyloidosis collected and frozen at -20C under a biobank IRB protocol were retrieved and sST2 measured. Patients were eligible for present study if they had a research sample collected within 90 days of their AL amyloidosis diagnosis. We have validated that values do not change significantly with storage at -20C over a 90 day period. Concentrations of sST2 were determined using a novel high-sensitivity sandwich immunoassay (Presagew ST2; Critical Diagnostics, San Diego, CA, USA). The sST2 assay had within-run and total coefficients of variation of <7.5% and 13.0% across its measurement range. Samples from 273 consecutive patients meeting diagnostic criteria for AL amyloidosis seen at our institution from 1/9/2010 to 12/22/2011 were evaluated. Median age was 63. 58% were male. One hundred and thirty have died over 33.9 months. Correlation between sST2 and the other biomarkers was modest with correlation coefficients of 0.48 and 0.20 for NT-proBNP and Troponin T, respectively. Patients with sST2 above and below the median of 27.2 ng/mL (6.3-596) had significant differences in 2 year overall survival: 71.2% to 39% (figure). In multivariate modeling sST2’s prognostic value was independent of the Mayo 2004 and the Mayo 2012 cardiac biomarker staging systems, the latter of which also includes prognostic information relating to plasma cell burden. In these multivariate models, sST2 median had a RR of 2.4, (95%CI 1.6, 3.6 p<0.001) with the Mayo 2004 Staging system (RR of 2.9, 95%CI 2.1, 4.1p<0.001); and sST2 median had a RR of 2.2 (95%CI 1.5, 3.4, p<0.001) with the Mayo 2012 staging system (RR 1.9, 95%CI 1.6, 2.3, p<0.001). A larger cohort including patients with longer follow up will be presented at the meeting as will gender specific cut off values and a comparison of our values with those previously used to prognosticate in patients with heart failure. sST2 appears to be a novel powerful prognostic factor for patients with AL amyloidosis. Because sST2 functions as a decoy receptor, which neutralizes the benefits of IL-33, it may play a role in the deleterious phenotype seen in patients with AL, i.e. myocardial hypertrophy and reduction of contractility. Disclosures: Saenger: Critical Diagnostics : Research Funding; Roche: Research Funding. Jaffe:Critical Diagnostics: Consultancy, Research Funding; Roche: Consultancy.

Abstract Background Multiple myeloma (MM) is a heterogeneous disease with variable responses to different therapeutic regimens and wide spectrum of survival. Much of the heterogeneity in the outcomes appear to be related to the underlying primary genetic abnormality, which in the majority of patients consist of either translocations involving the heavy chain region on chromosome 14 (IgH translocation) or trisomies of odd numbered chromosomes. We hypothesized that the response to lenalidomide (Len) therapy would vary significantly based on the underlying molecular subtype of myeloma. Methods We examined a cohort of 518 patients with available FISH results, who had been exposed to Len-based regimens. Medical records were reviewed and data regarding the best response and time to next therapy following treatment with Len-based regimen was obtained. Data from the first use of Len was collected. Len was given in combination with dexamethasone (Dex) with or without alkylators in combination. Patients who received a combination of IMiD and bortezomib as their first exposure to Len were excluded. Patients were grouped according to whether FISH showed a trisomy or an IgH translocation. Results The median age was 62 (28-91), and the median estimated follow up from diagnosis was 52 months (95% CI; 50, 54) with 359 (69%) alive at the time of analysis. An IgH translocation was seen in 129 (30%) of patients and a trisomy in 268 (62%) of patients. IgH translocations included t(11;14) in 92 (18%), t(4;14) in 45 (9%), t(14;16) in 21 (4%); 34 (8%) had both translocations and trisomies. For the current analysis, we included only patients with either a translocation or trisomy (n=397) excluding those with neither or both of the abnormalities. The median time to start of Len from diagnosis was 0 months (range, 0-64). A PR or better was seen in 80% of patients with trisomy compared with 63% of the patients with translocation (p<0.001); and the response rate was similar among the different translocation types. The median TTNT was 28 months among trisomy pts compared with 17 months for translocated patients (p<0.001, figure). The median TTNT was similar across the different types of translocations (Figure). Among this group, 134 patients proceeded to an autologous SCT after Len induction. Among these patients, no difference was seen in terms of TTNT (29 months for patients with translocation vs. 28 months for those with trisomy (p=0.8). Finally, the TTNT was no different if Len was used with Dex or as part of an alkylator combination. Conclusion The current data supports the hypothesis that the underlying primary genetic abnormality can affect the response to a particular therapy. In this study response to Len was significantly higher in myeloma with trisomy compared with IgH translocated myeloma. Although the routine use of combinations of a proteasome inhibitor plus Len in frontline therapy in all patients with myeloma may overcome the lower response rate in IgH translocated patients, in most countries such a regimen is not approved or economically feasible. Based on our study, newly diagnosed patients with evidence of trisomy on FISH could be considered for a Len-based regimen such as lenalidomide-low dose dexamethasone. Additional studies should examine if use of bortezomib in patients with IgH translocation will lead to better outcomes compared with Len based therapies. Disclosures: Lacy: Celgene Corporation: Research Funding. Gertz:Celgene: Honoraria. Dispenzieri:Celgene, Millenium, Jansenn, Pfizer: Research Funding. Kumar:Merck: Consultancy, Honoraria; Celgene: Consultancy, Research Funding; Millennium: The Takeda Oncology Company: Research Funding; Novartis: Research Funding; Genzyme: Research Funding.

Introduction With the introduction of novel agents, survival in multiple myeloma has successively increased in the past decade. This improved survival increases the risk for late complications. Patients continue to receive melphalan therapy as a standard induction for those over the age of 65. Lenalidomide is considered a standard component of induction therapy in the United States for patients who are transplant candidates. Stem cell transplantation remains the standard of care for patients eligible to receive it. As a consequence of exposure to lenalidomide, stem cell transplant, and melphalan, the risk of late myelodysplasia and acute leukemia remains significant. We reviewed the Mayo Clinic experience with therapy-induced myelodysplasia beginning with the advent of novel agents. Patients and Methods All patients that carry the diagnosis of multiple myeloma between January 1, 2000, and September 1, 2011, were included. Patients with a synchronous diagnosis of a myeloproliferative or a myelodysplastic disorder or those who developed the myelodysplastic disorder within 15 months of first chemotherapy exposure were excluded. The date of diagnosis for the purpose of this abstract was based on first exposure to chemotherapy and not first detection of a monoclonal protein or smoldering multiple myeloma. All patients had to have morphologic verification in the bone marrow of dysplastic change consistent with therapy-related myelodysplasia. Results Of 3111 patients who had a myeloma diagnosis and first treatment after January 1, 2000, through September 1, 2011, 22 patients were identified to fulfill the criteria of myelodysplasia. There were 13 men and 9 women with a median age of 67 (46 to 82). At the time of this report, 17 have died. Prior to the development of myelodysplasia, exposure to an alkylating agent, lenalidomide, or an auto stem cell transplant was seen in 13, 15, and 10, respectively. Only one patient had been exposed to lenalidomide alone. Eighteen patients were classified as myelodysplasia. Four had acute non-lymphocytic leukemia. Metaphase cytogenetics was available in 19 and only one was normal. Twelve were hypodiploid. Trisomy 8 or abnormalities of chromosome 5 and 7 were present in 13. Seven patients received a hypomethylating agent with no clear evidence of response in any. Four patients had an allotransplant to manage the MDS/AML and only one survives 487 days after a matched-related donor allogeneic transplant. The median time from initial therapy of multiple myeloma to recognition of MDS or AML was 50.9 months (range: 15.2-146.5 months) fig 1. The median overall survival of the 22 patients is 6.5 months. Fig 2 Six of the 22 had active myeloma at the diagnosis of MDS/AML. Conclusion Myelodysplasia during the era of novel agents is a devastating complication of therapy with a very short survival and low response rate. As a time-dependent complication, the overall risk cannot be accurately estimated but has occurred in <1% of our patient population to date. Hypomethylating agents were ineffective in the seven that received it. One of four allotransplant patients remains alive. Ongoing surveillance for MDS/AML in this population is warranted and more effective therapies are needed. Disclosures: Kumar: Onyx: Consultancy, Research Funding; Millennium: Consultancy, Research Funding; Celgene: Consultancy, Research Funding.

Abstract Abstract 2950 Background: The median age of patients diagnosed with MM is approximately 70 years, and it is a relatively uncommon disease in the younger population. Both conventional chemotherapy and stem cell transplantation (SCT) have favorably impacted the overall survival (OS) of young MM patients. The median survival of patients < 40 years of age, diagnosed prior to 1993 was reportedly 54 months at our institution. However, the impact of novel agents in this patient population is not well known. We studied the outcome of young patients presenting to our institution over the last decade. Methods: Records of 1538 patients presenting between 01/99 to12/08 were reviewed. The demographics, features and therapeutic interventions in patients up to 45 years of age at diagnosis were analyzed using descriptive statistics. The survival outcome of this group was compared with the remainder of the cohort using the Kaplan-Meier method. Results: One-hundred (6.5%) out of 1538 newly diagnosed MM patients were ≤ 45 years of age at diagnosis. The median follow-up of this group of young patients was 86 months. The disease and patient characteristics are outlined in table 1. A median of 5 regimens (range 1–14) was administered, and 85% patients had received high-dose therapy. 15 patients underwent allogeneic SCT after at least one prior autologous SCT. Novel agents were used both in the front-line and relapsed setting (lenalidomide 60%, thalidomide 56%, pomalidomide 9% and bortezomib 49%), and 45% of initial regimens were novel agent based. The 5 and 7-year OS from diagnosis was 69% and 59%, respectively and the median OS was 93 months. In contrast, the median OS of patients >45 years diagnosed during this period was 53 months (P=0.001, figure 1). Conclusion: A marked improvement in OS of young patients with MM diagnosed in the novel agent era is noted in comparison to the historical control of similar age group. In addition, the age associated survival benefit in the younger patient population prevails in the era of novel therapies. Disclosures: Gertz: Celgene: Honoraria. Lacy:Celgene: Research Funding. Dispenzieri:Binding site: Honoraria; Celgene: Research Funding. Kyle:Millennium: Consultancy; Binding Site: Honoraria. Kumar:Millennium Pharmaceuticals, Inc.: Research Funding; Celgene: Consultancy, Research Funding; Genzyme: Research Funding; Novartis: Research Funding; Merck: Consultancy, Honoraria.

Abstract Background Acquired factor X (FX) deficiency is associated with immunoglobulin light chain (AL) amyloidosis and may be accompanied by hemorrhage. There are limited data on the effects of autologous stem cell transplant (ASCT) on FX deficiency. We reviewed hemorrhagic complications and the effect of high dose melphalan (HDM) and ASCT on FX levels in AL amyloidosis patients with FX deficiency. Methods We conducted a retrospective chart review of patients with AL amyloid with FX levels below 60%, not on chronic anti-coagulation who underwent HDM/ASCT at the Mayo Clinic, Rochester, MN between 1995 and 2011. Results Forty-one of 358 patients (11%) met our study criteria. Median pre-ASCT FX was 45% (range: 2%, 59%). The most common bleeding complication was central line associated n=15 (37%) followed by gastrointestinal n=10 (24%) and genitourinary n=9 (22%). The most frequent and severe bleeding complications occurred in patients with FX levels less than 10%. Four patients required emergent splenectomy owing to splenic rupture; one of these patients died from hemorrhagic shock. Periprocedural prophylaxis included activated recombinant Factor VII (rFVIIa) infusions, fresh frozen plasma (FFP) infusions and platelet transfusions. rFVIIa was efficacious in controlling bleeding during splenectomy (n=5) and, in conjunction with arterial embolization, for retroperitoneal bleed (n=1). Elective splenectomy for FX deficiency (n=1) resulted in only transient improvement in FX level. No relationship between the degree of pre-ASCT FX deficiency and other laboratory values (alkaline phosphatase, AST, total bilirubin, serum albumin, total serum protein, serum creatinine, total urine protein, beta2 microglobulin, troponin T) was found. Post-ASCT FX levels were determined in seventeen patients. In four of these patients, post-ASCT FX levels were determined in the acute/subacute phase of ASCT before steady state FX levels could be achieved; the median change in FX for these patients was -6.5% (range: -19%, 3%). In the remaining thirteen patients, who were between 99 and 1920 days from ASCT, FX improved by median 26% (range: -15%, 92%). Overall post-ASCT FX increased in twelve of thirteen (92%) patients. The improvement in FX correlated with improvement in the degree of proteinuria (p = 0.04) and showed a trend towards significant correlation with improvement in serum alkaline phosphatase (p = 0.06). Conclusions Hemorrhagic complications are most frequent and severe for FX levels below 10%. rFVIIa infusions, FFP and platelets were effective prophylactic agents. In the single patient who underwent elective splenectomy, a transient improvement in FX level was seen. Splenectomy was otherwise reserved for patients with splenic rupture/hematoma. Post-ASCT FX levels increased in twelve (92.3%) of the remaining thirteen patients; five of the patients (38.5%) were no longer FX deficient after ASCT. The degree of improvement in FX levels was correlated with improvement in markers of renal or hepatic involvement by amyloid. Disclosures: Kumar: Celgene: Consultancy, Research Funding; Millennium: Consultancy, Research Funding; Onyx: Consultancy, Research Funding.

Abstract Background Pomalidomide (POM) is the newest Immunomodulatory agent (IMiDs) that has shown clinical efficacy in relapsed multiple myeloma (MM) refractory to lenalidomide (LEN) and thalidomide (THAL). Studies of MM cell microenvironment suggest that tumor subclones compete for dominance during changes in drug therapy. It was previously observed that a minor clonal population increased in prominence of MM cells after 1 year of treatment with LEN. We examined whether the patients having THAL or LEN as the most recent prior-line therapy affects response to POM. Methods We studied 208 patients enrolled in a phase II trial of POM / dexamethasone between November 2007 and March 2012 at Mayo Clinic, Rochester. We reviewed the immediate prior-line therapy before enrollment in our trial. Comparison of treatment duration of POM and response rates were conducted between patients who had either THAL or LEN as latest prior-line therapy, and patients who were treated with non-IMiDs immediate before enrollment in POM trial. Treatment duration of POM was estimated using Kaplan Meier method and the survival curves were compared using log-rank test. We used univariate Cox proportional hazard models to estimate the prognostic impact of different variables. Results The median age of patients was 63 (range from 32 to 88). 68 % were males. 80 patients (38.5%) had THAL or LEN immediate prior to POM. Median prior-line therapies were 3. Patients who received THAL or LEN immediately prior to POM had a lower response rate than those who had non-IMiDs as latest therapy (29% vs 44%, p 0.04) and shorter median duration of POM treatment (5.7 months vs 7.3 months, p 0.02). In 190 (91%) patients who were previously treated with LEN and THAL at any time, median time between the end of LEN or THAL treatment and the initiation of POM was higher for POM responders than non-responders (10 months vs 3 months, p 0.0008). Patients responded to POM had a shorter duration of prior LEN or THAL treatment compared to non-responders (9 months vs 15 months, p 0.001). Conclusion THAL or LEN as an immediate prior-line therapy to POM is associated with a lower response rate and shorter effective treatment duration. Longer interval between prior immunomodulatory compounds and POM, and shorter exposure to previous immunomodulatory compounds are associated with better POM treatment response. Disclosures: Gertz: Celgene: Honoraria. Kumar:Merck: Consultancy, Honoraria; Celgene: Consultancy, Research Funding; Millennium: The Takeda Oncology Company: Research Funding; Novartis: Research Funding; Genzyme: Research Funding. Lacy:Celgene Corporation: Research Funding.

Abstract Background Multiple myeloma (MM) is uncommon in patients below 40 years of age. Between 1960 and 1992 when stem cell transplantation (SCT) was rarely performed and novel agents were unavailable, overall survival (OS) was reported to be 54 months in the Mayo Clinic series of patients with MM below forty years of age. The impact of novel agents or SCT in this population is unclear. Herein, we report the outcomes of patients under 40 years of age who were evaluated over a span of more than five decades with a focus on the periods contemporaneous with the introduction of SCT and novel agents, the major therapeutic milestones in the management of MM. Methods We analyzed the medical records of patients with MM under 40 years of age who were evaluated at Mayo Clinic, Rochester, MN between 1/1/1960 and 12/31/2011. SCT and novel agents were utilized infrequently prior to the years 1990 and 2000, respectively. Patients were therefore divided into three cohorts by the year of diagnosis of MM: Group A (1960 -1979), Group B (1980 to 1999) and Group C (2000 –2011) to assess the impact of major therapeutic advances (i.e. Increased utilization of SCT and novel agents compared to conventional chemotherapy). OS was calculated by the Kaplan -Meier method. Results Out of 8063 unique MM patients seen at our institution during this period, 174 (2%) patients were under 40 years of age at diagnosis. The median age at diagnosis was 36 years (range: 19-39). The estimated median follow-up of the entire cohort was 179 months (95% CI: 149-196 months). The median OS of the entire cohort was 76 months (95% CI: 45-80 months) from diagnosis. The median OS of patients in Groups A (n=29, 17%), B (n=93, 53%), and C (n=52, 30% ) was 44 months (95% CI: 20- 76), 79 months (95% CI: 46-97), and 92 months (95% CI: 42-NR), respectively (p=0.005). No significant OS difference was noted between Groups B and C (Figure). Sixty-six (38%) patients underwent at least one SCT (autologous: 56 patients and allogeneic 10 patients). The utilization of SCT increased over the three time periods from Group A 0%, Group B 39% and Group C 58% (p<0.001). Of 153 patients in whom front-line therapy-related data were available 118 (77%) received conventional and 35(23%) received novel agents. The median OS of patients who underwent transplantation (n=66) was 93 months compared to 46 months for those who did not (n=108, p=.01). In the 66 patients who underwent SCT, the median OS was 93 months for conventional agents-based induction (95% CI: 73-143) versus 97 months (95% CI: 41-187) for novel agent based induction (p=.4). Sixty-eight (40%) patients received novel agents at some point during the course of their disease [bortezomib 35 (54%), thalidomide 44 (67%), lenalidomide 47 (71%) and pomalidomide 7(11%)]. The median survival of these patients was 131 (95% CI: 88-161) months versus to 46 (CI: 37-74) months for those (n=106) receiving conventional agents only (p=0.0002). Conclusions OS of patients with MM under 40 years of age in the pre-transplant era (Group A) was significantly shorter than that of patients diagnosed in the era of SCT (Group B) and SCT plus novel agents (Group C). Although improvement of survival outcomes is evident with utilization of novel agents, similar outcomes of Groups B and C indicate lack of incremental benefit over SCT with utilization of novel agents. Maximal survival gain coincides with the introduction of SCT in this unique patient cohort. Disclosures: Kumar: Celgene: Consultancy, Research Funding; Millennium: Consultancy, Research Funding; Onyx: Consultancy, Research Funding.

Abstract Background: Multiple myeloma (MM) is a heterogeneous disease with very divergent outcomes that are dictated in a large part by specific cytogenetic abnormalities, as well as other prognostic factors such as the proliferative rate of marrow plasma cells. Prognostic systems incorporating these factors have shown clinical utility in identifying high-risk patients, and are increasingly being utilized for treatment decision-making. However, the prognostic relevance of these factors may change with the application of novel therapies. The objective of this study was to determine the impact of risk-stratification (incorporating plasma cell metaphase cytogenetics, interphase fluorescent in-situ hybridization (FISH) and the slide-based plasma cell labeling index (PCLI)) in a cohort of patients with newly diagnosed MM treated initially with lenalidomide + dexamethasone (Rev-Dex). Methods: From March 2004 to November 2007, 100 consecutive patients treated with Rev (25mg/day) on days 1 through 21 of a 4-week cycle in combination with dexamethasone as initial therapy for newly diagnosed myeloma, were identified. High-risk MM was defined as presence of any one or more of the following: hypodiploidy, monoallelic loss of chromosome 13 or its long arm (by metaphase cytogenetics only), deletion of p53 (locus 17p13) or PCLI ≥ 3% or immunoglobulin heavy chain (IgH) translocations, t(4;14) (p16.3;q32) or t(14;16)(q32;q23) on FISH. PFS and OS survival estimates were created using the Kaplan Meier method, and compared by log-rank tests. Results: The median estimated follow-up of the entire cohort (N=100) was 36 months. The median PFS was 31 months; the median OS has not been reached. The 2- and 3-year OS estimates were 93% and 83%, respectively. 16% patients were deemed high-risk by at least one of the 3 tests (cytogenetics, FISH or PCLI). Response rates (PR or better) were 81% versus 89% in the high-risk and standard risk groups, respectively, P=NS; corresponding values for CR plus VGPR rates were 38% and 45% respectively. The median PFS was 18.5 months in high-risk patients compared to 37 months in the standard-risk patients (n=84), P<0.001(Figure). Corresponding values for TTP were 18.5 months and 36.5 months, respectively, P=<0.001. OS was not statistically significant between the two groups; 92% 2-year OS was noted in both the groups. Overall, 95 patients had at least one of the 3 tests to determine risk, while 55 patients could be adequately stratified based on the availability of all the 3 tests, or at least one test result that led to their inclusion in the high-risk category. The significant difference in PFS persisted even when the analysis was restricted to the 55 patients classified using this stringent criterion; 18.5 months vs. 36.5 months in the high-risk and standard- risk groups respectively; P<0.001. In a separate analysis, patients who underwent SCT before the disease progression were censored on the date of SCT to negate its effect, and PFS was still inferior in the high-risk group (p=0.002). Conclusion: The TTP and PFS of high-risk MM patients are inferior to that of the standard-risk patients treated with Rev-Dex, indicating that the current genetic and proliferation-based risk-stratification model remains prognostic with novel therapy. However, the TTP, PFS, and OS obtained in high-risk patients treated with Rev-Dex in this study is comparable to overall results in all myeloma patients reported in recent phase III trials. In addition, no significant impact of high-risk features on OS is apparent so far. Longer follow-up is needed to determine the impact of risk stratification on the OS of patients treated with Rev-Dex. Figure Figure

Abstract Abstract 615 Background: Trials comparing efficacy of standard melphalan prednisone (MP) therapy with MP plus thalidomide (T) in the transplant ineligible, elderly patients with multiple myeloma have provided conflicting evidence. While there is greater agreement with regard to superior response rates (RR) with the addition of T to MP in elderly patients, the impact on progression free survival (PFS) and overall survival (OS) is less clear with some trials showing an improvement in PFS and/or OS with MPT and others demonstrating no difference in outcomes. We performed a systematic review to integrate the existing outcome data related to the efficacy of MP vs. MPT using a meta-analytic approach. Methods: A comprehensive search of electronic database through July 31st, 2009 was performed for publications, abstracts and presentations to identify randomized controlled trials (RCTs) comparing MP with MPT. A meta-analysis was performed by pooling results on clinical endpoints of RR, PFS and OS reported in all the identified RCTs under a random effects model. We did not have access to individual patient data from these trials. Results: Overall, five prospective RCTs (3 published articles and 2 abstracts) comparing MP with MPT regimen and comprising a total of 1571 patients were identified. For the endpoints of OS and PFS, data were extractable only from 4 RCTs (abstract by Gulbrandsen et al. was excluded). The Bregg and Egger funnel plot for OS demonstrated a symmetric distribution (P = 0.6) indicating no significant publication bias. The test of heterogeneity among all RCTs was statistically significant in the estimate of RR (tau2=0.21; chi2=16.33; p=0.003 (df=4); I2 = 75.5%), but not significant for the estimates of PFS (tau2=0.01; chi2=4.61; p=0.2 (df=3); I2 = 34.9%), and OS (tau2=0.02; chi2=5.53; p=0.14 (df=3); I2 = 45.8%). As expected, the pooled odds ratio of responding to treatment with MP versus MPT was 0.307 (P&lt;0.001) indicating that MP was worse than MPT in achieving at least a partial response. The pooled hazard ratios (HR) for PFS and OS were 1.59 (p&lt;0.001) and 1.34 (p=0.006), respectively (see table for forest plots) in favor of MPT. Conclusion: Our meta-analysis implies that in previously untreated, transplant ineligible elderly patients with multiple myeloma, the addition of thalidomide to melphalan-prednisone demonstrates improved RR, PFS and OS compared with the use of melphalan-prednisone alone. Although the results from a comprehensive individual patient data pooled analysis would give a more precise estimate, our analysis suggests that MPT is superior to MP in terms of response and survival. Disclosures: Dispenzieri: Celgene: Research Funding. Gertz:Celgene: Honoraria. Kumar:celgene, genzyme, millennium, novartis, bayer: Research Funding; genzyme: Membership on an entity's Board of Directors or advisory committees.

Abstract Background The presence of circulating plasma cells (PCs) in multiple myeloma (MM) is a known poor prognostic marker. Prior studies have utilized a technically challenging slide-based immunofluorescence technique to detect and quantify the presence of circulating PCs which was not widely adapted in clinical practice. More recently, the routine use of flow cytometry has provided the opportunity to quantitatively assess circulating PCs in MM patients with relative ease. We report the prognostic value of quantifying circulating clonal PCs using multiparametric flow cytometry in MM patients with relapsed disease. Methods We evaluated all MM patients seen at the Mayo Clinic, Rochester from 2009 to 2011 with previous or ongoing relapsed disease and who had their peripheral blood samples evaluated by flow cytometry. Each blood sample had its peripheral blood mononuclear cells isolated by ficoll gradient and stained with antibodies to CD45, CD19, CD38, CD138 and cytoplasmic Kappa and Lambda Ig light chains. A six-color multi-parameter flow cytometer (Becton Dickinson FacsCantos II) was used to examine each sample with a target of detecting 150,000 events (cells) that was then analyzed using the Facs Diva Software. Plasma cells were selectively analyzed through combinatorial gating using light scatter properties and CD38, CD138, CD19, and CD45. Normal PC's were then separated from clonal plasma cells based on the differential expression of CD45, CD19 and polytypic Ig light chains. The clonal plasma cells detected were reported out as the number of clonal events/150,000 collected total events. For those samples where less than 150,000 events were gated or examined, the number of final clonal events was adjusted to 150,000 events. Survival analysis was performed by the Kaplan-Meier method and differences in survival assessed using the log rank test. Results There were 647 consecutive patients with a history of treated MM who had a peripheral blood flow cytometry as part of their routine clinical evaluation. The median patient age was 62 years (29-88) and 55% were male. The median time since diagnosis was 12 months (range: 1-363) and the median number of lines of treatment received was 2 (1-11). There were 81 (13%) patients with clonal circulating PCs with a median of 368 cells (4 – 133,464). The 2-year overall survival (OS) for the 81 (13%) patients with any circulating PCs was 17% compared with 65% for those with none (P<0.001). The presence of circulating clonal PCs was associated with high-risk disease by FISH (P <0.001) as well as higher PCLI (P <0.001). We then correlated the presence of circulating clonal PCs with the disease status at flow cytometry assessment. Among the study patients, only 145 (22%) had actively relapsing disease with the remaining 502 (78%) in a plateau including patients in CR. Circulating clonal PCs were more likely to be detected in patients with actively relapsing disease compared with plateau phase (43% vs. 4%, P < 0.001); none of the CR patients and <5% of the remaining plateau phase patients had any detectable circulating clonal PCs. We then restricted the analysis to the actively relapsing patients; the best cutoff predicting 1-year mortality by ROC analysis was 100 events. Based on this, we defined >=100 events as a cutoff for defining the prognostic role of circulating clonal PCs in actively relapsing patients. The median OS for those with >=100 clonal PC events was 12 months compared with not reached for those with <100 events (p<0.001; Figure 1 ). Among patients with actively relapsing disease, >= 100 circulating PCs was associated with a higher ISS stage, plasma cell labeling index and bone marrow PC% compared with those with <100 circulating PCs. In a multivariable model, only LDH > 222 (HR: 2.08, P = 0.045) and >= 100 circulating PCs (HR: 2.48, P = 0.048) were found to adversely affect OS in actively relapsing patients. Conclusion The utilization of flow cytometry to quantify circulating clonal PCs in patients with relapsed MM appears to have significant prognostic relevance. In patients with actively relapsing disease, >= 100 circulating PCs predicted for worse OS with a median of 12 months. Future studies are needed to determine if this would allow an opportunity to develop a more risk adapted approach for patients with relapsed disease. Disclosures: Kumar: Celgene: Consultancy, Research Funding; Millennium: Consultancy, Research Funding; Onyx: Consultancy, Research Funding.