ALBERT

Description: A functional BCR is essential for survival of normal B-cells, in response to cognate antigen or tonic, antigen-independent stimuli. Cross-linking of BCR by antigen triggers key phosphorylation events in the early signalosome. Mammalian wild type BRAF, a member of the RAF cytosolic kinase family (A-RAF, B-RAF, C-RAF) is critical to BCR function, mediating RAS-RAF-MEK-ERK or mitogen-activated protein kinase (MAPK) pathway signal transduction, via phosphorylation of ERK1/2. The MAPK pathway is a central conduit for survival and proliferation. Importantly, use of inducible deletion models have shown that wild type BRAF is the predominant kinase that transduces BCR signals to activate ERK1/2, with C-RAF playing an accessory role and A-RAF displaying a x20-30 fold lower basal activity in ERK1/2 stimulation. Tonic BCR survival signals in normal B-cells are also transduced via phosphorylation of ERK1/2, but do not require antigen stimuli. Whether the BCR plays a comparable role in sustaining survival in malignant B-cells is less well characterized and remains a central question in understanding the origins and progression of mature B-cell neoplasms. Hairy cell leukaemia (HCL) is a rare B cell leukaemia with characteristic hair-like cytoplasmic projections on tumor cells, displaying distinctive activation markers. A striking feature of monoclonal HCL tumors is expression of multiple variant immunoglobulin heavy chain (sIgH) isotypes as components of the BCR on individual tumor cells, defining the major subset of disease (mult-HCL). Most mult-HCL tumors exhibit IGV somatic hypermutation with a low level of on-going mutations and AID expressed, implicating initial contact with antigen via the BCR. The functional relevance of the BCR to transformation and survival however has as yet not been mapped in HCL. Seminal exome sequencing data in typical HCL identified mutant BRAF V(600)E as almost universal in this tumor. Consistent with mutant BRAFV(600)E, levels of phosphorylated ERK (p-ERK) are raised in hairy cells. As there is an essential requirement for wild type BRAF in transducing BCR signals, the question arises how mutant BRAF may affect BCR function in HCL, given requirements for dimerization of wild type BRAF for ERK1/2 activation, and whether ERK1/2 activation can be enhanced by functional BCR signals for downstream effector signals in HCL. To examine this, we evaluated BCR signalling in mult-HCL (n=10), in cases uniformly displaying mutated BRAF and IGHV genes. Two apparent functional sets were delineated by IgD co-expression. In sIgD+ mult-HCL, IgD mediated persistent Ca2+ flux, which was also evident via 〉1 sIgH isotype, linked to increased ERK1/2 activation and BCR endocytosis (4/4 cases). In sIgD-vemult-HCL however (6/6 cases), BCR-mediated signals activating ERK1/2 for downstream effects were restricted to a single sIgH isotype, with sIgM notably dysfunctional and remaining immobilised on the cell surface. These observations reveal a clear discordance between expression and function of individual isotypes in mult-HCL. In dual sIgL expressing mult-HCL (3/3 cases), only a single sIgL was fully functional. We next examined effects of anti-BCR stimuli on mult-HCL tumor cell survival ex-vivo. Significantly, all functional non-IgD isotypes increased ERK1/2 phosphorylation but triggered apoptosis of tumor cells, in both sets (4/4 cases) to establish a consistent outcome in these replicate cases. IgD stimuli, in marked contrast retained tumor viability with no evidence for pre-apoptotic effects (2 cases; 1 mult-HCL and 1 sIgD only-HCL). Despite mutant BRAF, BCR signals amplify ERK1/2 phosphorylation, but isotype dictates functional downstream outcomes. In mult-HCL lacking IgD, a role for antigen in stimulating the BCR for tumor persistence appears unlikely. It remains feasible that mutant BRAF in these cases retains tonic signals through activated ERK1/2 for survival, but this remains speculative at present. Surface IgD emerges with potential to transduce BCR signals for tumor survival and persistence in-vivo, but given its enigmatic role even in normal B-cells, its relevance to HCL progression is unclear. These observations raise the possibility that mutant BRAF may be a mechanism to bypass any antigen-dependent BCR signalling constraints in mult-HCL. Disclosures: No relevant conflicts of interest to declare.

Description: Abstract 2642 Introduction With the aging of the population clinicians are increasingly confronted with elderly, often frail, patients with a DLBCL. While the very elderly patients, defined by the age of ≥75 year, are often excluded from clinical trials, only few prospective data in the rituximab-era are available on the outcome in this patient cohort. To asses efficacy, tolerability and safety of standard intensive rituximab-containing therapy in those patients, a descriptive population-based, cohort study was performed. Detailed information on treatment, toxicity and outcome in all patients aged ≥75 year, diagnosed with DLBCL in the Dutch province Friesland was prospectively gathered and analyzed. Methods Since 2005 all patients diagnosed with a haematological malignancy in Friesland, a province with 600.000 inhabitants, are prospectively registered and followed in a population-based registry, the HemobaseR. For this analysis data of all patients aged ≥ 75 years with a newly diagnosed DLBCL over a period of six years were retrieved from the HemobaseR. Data of clinical characteristics, treatment and its adaptations, treatment-related toxicity and outcome were obtained. Treatment modality was divided in four groups: R-CHOP chemotherapy, other rituximab-containing therapy, palliative radiotherapy and only supportive care. Follow-up was completed until 31 December 2011. Cox Proportional hazards model was used for identifying significant prognostic risk factors. Kaplan-Meier curves for each group were evaluated by a logrank test. Results From 2005 until the end of 2011 103 patients aged ≥ 75 years were diagnosed with a DLBCL. The median age was 81 years (range 75 – 96) with a slight female predominance (57%). The median observation period was 13 months (range 1 – 78) and 31 months for those still alive at time of evaluation.19 patients (19%) had stage 1 disease; in 74 patients (71%) advanced disease (stage 2–4) was reported and in 10 patients (10%) staging was incomplete. In 84 patients (81%) an age adjusted International Prognostic Index was calculated, 43% of them had an aaIPI of 2 or 3. Of the patients with stage 1 disease, 13 (68%) received three courses of R-CHOP and radiotherapy with a curative intent. Eight (62%) of them did complete this therapy. Of the other 84 patients 57 (68%) received R-CHOP chemotherapy with a curative intent. 31 (54%) of them completed at least six cycles. Ultimately 39 patients (56%), who did start with a standard therapy regimen, completed their treatment. A complete remission was achieved in 30 patients (77%). In the remaining group 10 patients (10%) received alternative, suboptimal, rituximab-based chemotherapy, 9 (9%) of patients was treated with radiotherapy. In 12 patients (11%) only supportive care was given. Severe toxicity (grade 3–4), occurred in 66% of all patients treated with rituximab-containing chemotherapy. Toxicity grade 3–4 was the main reason for receiving less then six cycles of chemotherapy (44%). Ten toxicity-related deaths (13%) were observed in patients treated with R-CHOP, with eight deaths due to infectious complications. The two-year survival was 67% for the elderly who completed chemotherapy, 25% for those treated with incomplete or inferior chemotherapy regimens and 20% for those receiving palliative radiotherapy or supportive care. In a multivariate analysis completing therapy and not age was significantly associated with a better survival (p

Description: Abstract 3656 Introduction Diffuse large B-cell lymphoma (DLBCL) is predominantly diagnosed in the elderly and its incidence is therefore rapidly increasing. Rituximab in combination with cyclophosphamide, doxorubicin, vincristine and prednisone (R-CHOP) is the standard treatment for patients with newly diagnosed DLBCL. This is mainly based on data from carefully controlled randomised trials with strict eligibility criteria. Therefore data reflecting the “real world” in the rituximab era are sparse. We conducted an observational prospective cohort study to identify whether comorbidity is an independent risk factor for overall survival (OS) in patients with newly diagnosed DLBCL treated with R-CHOP with curative intent. Methods All patients with newly diagnosed DLBCL in Friesland, a Dutch province, are prospectively registered by their clinicians in a population-based registry (HemoBase®) since January 2005. Patients ≥18 years, CD20 positive, Ann Arbor stage II-IV were included if they received ≥ one cycle of R-CHOP. Clinical variables registered were age, gender, performance status (PS), Ann Arbor stage, presence of B-symptoms, lactate dehydrogenase, bulky disease, number of extranodal sites involved. Comorbidity was scored using the Charlson Comorbidity Index (CCI) [Charlson et. al.; J Chron Dis, 1987]. The score is a summation of the number of comorbidities existing at the time of diagnosis. The group was divided in low CCI (0–1) and high CCI (≥2). The primary endpoint was OS, defined as start of diagnose of DLBCL until death by any cause. Cox Proportional hazards model was used to identify significant risk factors. Variables used to calculate International Prognostic Index (IPI) and CCI were entered into the model. Kaplan-Meier curves were evaluated by log-rank test. Results Over a period of 7 years 302 patients were newly diagnosed with DLBCL after the start of the HemoBase® registry. Of those patients, 76 received no R-CHOP therapy, 9 had unknown Ann Arbor stage and 61 had Ann Arbor stage I. Therefore data from 156 patients could be retrieved from the population-based registry for further analysis. The median age was 69 years (range 23 – 93). The median observation period for the total population was 24 months (range 0 – 83) and for patients still alive 33 months (range 2 – 83). Twenty-five percent of patients had a PS≥2, 39% had IPI≥3. The percentage of patients with 8, 7, 6, 5, 4, 3, 2, or 1 R-CHOP cycle(s) given were 49, 3, 32, 1, 3, 4, 2, 6 respectively. R-CHOP21 was given to 74% and R-CHOP14 to 26%. Dose reduction of 20% or more in doxorubicin, cyclophosphamide or vincristine occurred in 26, 19, and 36% of the patients respectively. In 54% of the patients dose reduction occurred in one or more antineoplastic drugs. Twenty-five patients had a CCI≥2. Most frequently observed comorbidities in the CCI≥2 group were diabetes (36%), peripheral vascular disease (32%), chronic pulmonary disease or second tumor (28%), myocardial infarction (24%), congestive heart failure or cerebrovascular disease (16%). The percentage of patients with a CCI score of 2, 3, 4 or 5 were 64, 28, 4 and 4% respectively. In the CCI≥2 group only 16% of the patients had also a PS≥2. Three year OS in the total study population was 68%: in patients with CCI

Description: Abstract 799 Background: Aggressive systemic mastocytosis (ASM) and mast cell leukemia (MCL) with or without an associated clonal hematologic non-mast cell lineage disease (AHNMD) are myeloproliferative neoplasms (MPN) with inadequate treatment options. The activating KIT D816V mutation occurs in ≈80% of patients (pts) with these advanced forms of SM and is central to disease pathogenesis. Midostaurin is an oral inhibitor of multiple tyrosine kinases, including wild-type and D816-mutated KIT. Promising results of an investigator-initiated trial (Gotlib et al. Blood. 2010;116:316) led to initiation of this multicenter phase 2 study (NCT00782067) of midostaurin in pts with advanced SM. Here, we report the efficacy and preliminary safety results of stage 1 of this trial. Methods: Midostaurin (100 mg BID) was administered continuously in 28-d cycles until progression or intolerable toxicity. Enrollment into an extension phase was permitted if the null hypothesis of an overall response rate (ORR) ≤ 30% was rejected per Fleming 2-stage design. Pts were required to have ≥ 1 measurable C-finding(s) (CF; eg, cytopenias, liver dysfunction) considered related to SM. The primary endpoint was ORR (major response [MR] + partial response [PR] according to Valent criteria) occurring in the first 6 cycles and maintained for ≥ 8 weeks (wk). International Working Group criteria for myelodysplastic syndrome (MDS; with slight modifications) were used to evaluate changes in transfusion dependence. Results: 62 pts were enrolled in stage 1, of whom 40 (65%) were eligible for efficacy evaluation. Reasons for ineligibility included absence of measurable CF (n = 11) or CF considered unrelated to SM (n = 11). Median age of eligible pts (25 males, 63%) was 64.5 y (range: 48–80 y). 33 (83%) pts had ASM (27 with an AHNMD) and 7 (18%) had MCL (3 with an AHNMD). AHNMDs (n=30) included 10 chronic myelomonocytic leukemia (CMML), 10 MDS/MPN-unclassified (MDS/MPN-u), 4 hypereosinophilic syndrome/chronic eosinophilic leukemia (HES/CEL), and 6 other subtypes. 22 (55%) pts received at least 1 prior therapy (median: 1.5; range: 1–4). 28 (70%) pts were KIT D816V/Y–positive, 3 (8%) were KIT D816V/Y–negative, and 9 (23%) were not evaluable for mutation status. The ORR was 60% (24/40), and most responses were MRs (21/24; Table). With a median follow-up of 27 months (mo), the median duration of response and median overall survival (OS) have not been reached. Of the 7 pts with MCL, 4 (57%) achieved an MR, including 3 ongoing incomplete remissions (IR) (19+ mo in 2 pts and 32+ mo in 1 pt). The OS in MCL pts was 22.6 mo. Additionally, 3 of 4 responding ASM/MCL-HES/CEL pts exhibited resolution of blood eosinophilia (mean baseline % and absolute eosinophils: 64% and 15.6 × 109/L). Median change in serum tryptase level among the 40 pts was −61% (range: −97% to 16%), with 16 (40%) pts exhibiting a ' 50% reduction lasting ≥ 8 wk. Median change in marrow mast cell (MC) burden in 32 evaluable pts was −41% (range: −92% to 83%), with 15/32 (47%) pts exhibiting a ≥ 50% reduction. All 62 pts received at least 1 dose of midostaurin and were included in the safety analysis. Grade 3/4 hematologic adverse events (AEs) considered drug-related were neutropenia (11%), anemia (3%), and thrombocytopenia (3%). The most common grade 3/4 drug-related non-hematologic AEs were fatigue (6%), nausea (6%), vomiting (5%), diarrhea (5%), and increased lipase (5%). As of March 15, 2012, therapy was discontinued in 26/40 pts: 7 for AEs (5 drug-related), 12 for disease progression, and 7 for other reasons. 3 of 30 pts with an AHNMD (2 CMML and 1 MDS/MPN-u) developed AML. Conclusion: In advanced SM pts, midostaurin was well tolerated and demonstrated a high rate of durable responses, including in MCL, which historically has a dire prognosis. The drug can produce significant reductions in MC burden, indicating the potential for disease modification. The stage 1 ORR was sufficient to reject the null hypothesis and permitted enrollment in the extension phase, where full accrual of 116 pts has been completed. Disclosures: Gotlib: Novartis: Membership on an entity's Board of Directors or advisory committees, Research Funding. George:Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees. Akin:Novartis: Consultancy. Sotlar:Novartis: Consultancy. Awan:Allos Therapeutics: Speakers Bureau. Morariu:Novartis: Employment. Squier:Novartis: Employment. Villeneuve:Novartis: Employment. Emery-Salbert:Novartis: Employment. Horny:Novartis: Consultancy. Valent:Novartis: Consultancy, Honoraria. Reiter:Novartis: Consultancy, Honoraria.

Description: In many B-cell lymphomas, chromosomal translocations are biologic and diagnostic hallmarks of disease. An intriguing subset is formed by the so-called double- hit (DH) lymphomas that are defined by a chromosomal breakpoint affecting the MYC/8q24 locus in combination with another recurrent breakpoint, mainly a t(14;18)(q32;q21) involving BCL2. Recently, these lymphomas have received increased attention, which contributed to the introduction of a novel category of lymphomas in the 2008 WHO classification, “B cell lymphoma unclassifiable with features intermediate between DLBCL and BL.” In this review we explore the existing literature for the most recurrent types of DH B-cell lymphomas and the involved genes with their functions, as well as their pathology and clinical aspects including therapy and prognosis. The incidence of aggressive B-cell lymphomas other than Burkitt lymphoma with a MYC breakpoint and in particular a double hit is difficult to assess, because screening by methods like FISH has not been applied on large, unselected series, and the published cytogenetic data may be biased to specific categories of lymphomas. DH lymphomas have been classified heterogeneously but mostly as DLBCL, the majority having a germinal center phenotype and expression of BCL2. Patients with DH lymphomas often present with poor prognostic parameters, including elevated LDH, bone marrow and CNS involvement, and a high IPI score. All studies on larger series of patients suggest a poor prognosis, also if treated with RCHOP or high-intensity treatment modalities. Importantly, this poor outcome cannot be accounted for by the mere presence of a MYC/8q24 breakpoint. Likely, the combination of MYC and BCL2 expression and/or a related high genomic complexity are more important. Compared to these DH lymphomas, BCL6+/MYC+ DH lymphomas are far less common, and in fact most of these cases represent BCL2+/BCL6+/MYC+ triple-hit lymphomas with involvement of BCL2 as well. CCND1+/MYC+ DH lymphomas with involvement of 11q13 may also be relatively frequent, the great majority being classified as aggressive variants of mantle cell lymphoma. This suggests that activation of MYC might be an important progression pathway in mantle cell lymphoma as well. Based on clinical significance and the fact that no other solid diagnostic tools are available to identify DH lymphomas, it seems advisable to test all diffuse large B-cell and related lymphomas for MYC and other breakpoints.

Description: Background Patients (pts) with advanced SM, including aggressive SM (ASM) and mast cell leukemia (MCL), often exhibit debilitating mediator symptoms and impaired quality of life (QoL) due to mast cell degranulation and organ damage. Limited treatment options are available for these poor-prognosis conditions. Midostaurin is an oral inhibitor of multiple tyrosine kinases, including wild-type and D816-mutated KIT. In vitro studies have shown that midostaurin inhibits growth and mediator release in human mast cells and basophils. Previously reported results from stage 1 of the ongoing phase 2 study in pts with advanced SM (D2201/NCT00782067; n = 40) showed a high (60%) overall response rate and good safety profile (Gotlib, et al. ASH 2012). Here, we report QoL results and updated duration of response and overall survival (OS) data for these 40 pts. Methods Midostaurin (100 mg twice daily [BID]) was administered continuously in 28-d cycles until progression or unacceptable toxicity. Responses and eligibility were adjudicated by a study steering committee using modified Valent criteria. Symptoms and QoL were assessed at baseline and after each treatment cycle with the Memorial Symptom Assessment Scale (MSAS; ranging from 0 [no symptoms] to 4 [maximum symptom frequency, severity, and distress]) and the Short-Form Health Survey (SF-12; ranging from 0 [worst] to 100 [best]). The total MSAS score (TMSAS), the global distress index score (GDI), the physical score (PHYS), and the psychological score (PSYCH) were derived from the frequency, severity, and distress values of selected symptoms and summarized for the MSAS questionnaire. The composite physical (PCS) and mental health (MCS) scores were summarized for the SF-12 questionnaire. Scores 〉 50 in the PCS and MCS represent above-average health status. Median values were computed at baseline and for the best value on treatment. In addition, the prevalence of the most frequent symptoms at baseline and at the time of the best TMSAS value was calculated. Results With a median follow-up of 35 mo for all pts (range, 20-46 mo), the median duration of response was 37 mo in the 24 responders (Table). Median OS was 41 mo in the 40 stage 1 pts and not reached in MCL pts. The median best reductions in symptom burden on treatment were 65%, 80%, 68%, and 77% as measured by the TMSAS, GDI, PHYS, and PSYCH assessments, respectively. Compared with baseline, 32% of 37 assessable pts had a 〉 50% improvement in TMSAS lasting more than 6 cycles, 35% in GDI, 27% in PHYS, and 30% in PSYCH, reached at a median time of 142, 114, 59, and 91 days, respectively. The 6 most prevalent symptoms at baseline were lack of energy, drowsiness, diarrhea, bloating, difficulty concentrating, and difficulty sleeping. The prevalence of all 6 was reduced on treatment from −17% for difficulty sleeping to −35% for bloating. The median PCS and MCS scores at baseline were 36 and 45 compared with 45 and 59, respectively, on treatment. Similar trends were observed in responders, indicating substantial physical and mental improvement. QoL was improved and symptom burden reduced in both pts with ASM and MCL. Conclusion In pts with advanced SM, midostaurin demonstrates a high rate of durable responses that are associated with improvement of disease-related symptoms and QoL. These data are the first systematic analyses of symptom burden and QoL changes with any therapy for ASM and MCL. Disclosures: Gotlib: Novartis: Membership on an entity’s Board of Directors or advisory committees, Research Funding, travel support Other. Off Label Use: This abstract describes a clinical trial evaluating the investigational agent midostaurin for use in patients with advanced systemic mastocytosis. George:Novartis: Consultancy, Membership on an entity’s Board of Directors or advisory committees. Akin:Novartis: Consultancy. Sotlar:Nanostring: Honoraria; Novartis: laboratory services compensation, laboratory services compensation Other. Hermine:AB Science: Consultancy, Equity Ownership, Patents & Royalties; Novartis: Research Funding; Celgene: Research Funding. Awan:Lymphoma Research Foundation: Research Funding; Spectrum Pharmaceuticals: Speakers Bureau. Mauro:Novartis: Consultancy, Honoraria, Research Funding; Bristol-Myers Squibb: Consultancy, Honoraria, Research Funding; Ariad: Consultancy, Honoraria, Research Funding, Speakers Bureau; Pfizer: Consultancy, Honoraria, Speakers Bureau. Morariu:Novartis: Employment. Squier:Novartis: Employment. Villeneuve:Novartis: Employment. Emery-Salbert:Novartis: Employment. Coombs:Novartis: Employment, Equity Ownership. Hartmann:Novartis: member of a Steering Committee Other. Horny:Novartis: Consultancy. Valent:Novartis: Consultancy, Honoraria, Research Funding. Reiter:Novartis: Consultancy, Honoraria.

Description: The prognostic impact of minimal residual disease (MRD) was analyzed in 259 patients with mantle cell lymphoma (MCL) treated within 2 randomized trials of the European MCL Network (MCL Younger and MCL Elderly trial). After rituximab-based induction treatment, 106 of 190 evaluable patients (56%) achieved a molecular remission (MR) based on blood and/or bone marrow (BM) analysis. MR resulted in a significantly improved response duration (RD; 87% vs 61% patients in remission at 2 years, P = .004) and emerged to be an independent prognostic factor for RD (hazard ratio = 0.4, 95% confidence interval, 0.1-0.9, P = .028). MR was highly predictive for prolonged RD independent of clinical response (complete response [CR], complete response unconfirmed [CRu], partial response [PR]; RD at 2 years: 94% in BM MRD-negative CR/CRu and 100% in BM MRD-negative PR, compared with 71% in BM MRD-positive CR/CRu and 51% in BM MRD-positive PR, P = .002). Sustained MR during the postinduction period was predictive for outcome in MCL Younger after autologous stem cell transplantation (ASCT; RD at 2 years 100% vs 65%, P = .001) and during maintenance in MCL Elderly (RD at 2 years: 76% vs 36%, P = .015). ASCT increased the proportion of patients in MR from 55% before high-dose therapy to 72% thereafter. Sequential MRD monitoring is a powerful predictor for treatment outcome in MCL. These trials are registered at www.clinicaltrials.gov as #NCT00209222 and #NCT00209209.

Description: Abstract 2677 Introduction: The percentage of proliferating cells evaluated on diagnostic tumor samples has been shown to be of high prognostic relevance in Mantle Cell Lymphoma (MCL) patients. As MCL is relatively rare, evaluation of proliferation has so far mostly been based on smaller patient cohorts that were retrospectively collected and inhomogenously treated. In 2004, the European MCL Network initiated two large European randomized trials for younger (“MCL Younger” trial) and older (“MCL Elderly” trial) MCL patients, primary results of which have recently been reported (Kluin-Nelemans et al., NEJM 2012, Hermine et al., ASH 2010). We aimed to clarify the prognostic relevance of the proliferation marker Ki-67 using pooled data from these two trials. Patients and Methods: Patients with histologically confirmed and previously untreated MCL of stages II-IV up to 65 years of age were randomly assigned in “MCL Younger” to either 6 cycles R-CHOP followed by myeloablative radio-chemotherapy and autologous stem cell transplantation (ASCT), or 6 cycles alternating R-CHOP/R-DHAP followed by high-dose-Ara-C containing conditioning and ASCT. Patients aged 60 years or older and not eligible for high-dose therapy were randomly assigned in “MCL Elderly” to either 8 cycles of R-CHOP or 6 cycles of R-FC; responding patients were subsequently randomized to either interferon-alpha or rituximab maintenance until progression. Histological diagnosis was confirmed by central review within the European MCL Pathology Panel. The percentage of Ki-67 positive cells was counted on diagnostic lymphoma samples among 2 times 100 cells by the central pathology labs according to published consensus guidelines (Klapper et al., J Hematopathology 2009). The outcome measures were time to treatment failure (TTF) from treatment initiation to stable disease, progression, or death from any cause, and overall survival (OS) from trial registration to death from any cause. We investigated the prognostic value of proliferation as a quantitative marker with regards to TTF and OS in univariable Cox regression and evaluated the previously established cut-off values of 10% and 30% (Determann et al., Blood 2008) using Kaplan-Meier estimates and log rank tests. We also adjusted for clinical prognostic factors (MIPI, Hoster et al., Blood 2008). Results: Counted Ki-67 values were available in 51% (543) of 1057 randomized patients (material not available, 30%; Ki-67 evaluation not possible due to technical reasons, 16%). The origin of tumor tissue was lymph node in 81%, gastrointestinal tract in 12%, bone marrow in 4% and other in 3%. The median proliferation rate was 20% (range, 0–97%; interquartile range, 12–34%) and did not significantly differ between tissue origins. In univariable analysis, a 10% higher proliferation rate was associated with hazard ratios of 1.18 (95% confidence interval, 1.12 to 1.25, p

Description: Abstract 1567 The B-cell receptor (BCR) is critical to survival of normal B-cells, and regulates key aspects of cellular behavior. Of these, response to antigen determines pathways of normal B-cell maturation, including isotype switch events that occur by deletional class switch recombination (CSR), an irrevocable event, to yield IgG/A memory B-cells. Less frequently, CSR via a cryptic site generates IgD+ B-cells whereas IgM+IgD+ antigen experienced B-cells synthesize each isotype by an alternative transcript splicing mechanism. The role of the BCR in survival of malignant B-cells however is less well defined, in particular in response to antigen. Intriguingly, in Hairy cell leukemia (HCL), BCR assembly occurs with multiple surface immunoglobulin (sIg) isotypes (mult-HCL), many co-expressed on individual hairy cells (HCs) in an otherwise monoclonal tumor. Multiple isotypes appear to exclude deletional CSR events, and suggests a RNA processing mechanism of molecular assembly. This phenotype is rare even amongst malignant B-cells, and raises the question of the functional relevance of individual variant isotypes. It also potentially presents a model to dissect roles of multiple isotypes on single B-cells. To examine this, we investigated the BCR in CD19+CD11c+CD103+ mult-HCL cases (n=10), in which 2–4 differing sIg isotypes were present on most HCs, with single or, in 3 cases, dual sIgL expression. In all cases, IGHV genes were mutated, and confirmed monoclonality. Phenotype revealed 2 distinct subsets by sIg isotype co-expression, IgD+ve and IgD-ve. Using Ca2+ flux and ERK phosphorylation assays after cross-linking with specific anti-sIg antibodies, we observed a functional BCR in all mult-HCL examined, in both subsets (10/10 cases Ca2+, 6/6 cases ERK). However, striking differences emerged between the two subsets. In sIgD+ve mult-HCL, IgD mediated persistent Ca2+ flux, with flux also evident via 〉1 sIgH isotype. In marked contrast, in sIgD-ve mult-HCL Ca2+ flux was restricted to a single sIgH isotype, but not via IgM. Flux signals in this subset were transient. In most cases only a single sIgL transduced flux. We next evaluated BCR endocytosis after cross-linking individual isotypes and IgL. In 2 sIgD+ve cases, anti-IgD and anti-Igλ stimulation led to endocytosis of both sIgD and sIgλ, and in 1 case, where examined, anti-IgM stimulation endocytosed both sIgM and sIgλ. In 3 sIgD-ve cases, functional sIgH and sIgL induced endocytosis of the stimulated isotype, but again sIgM was dysfunctional, remaining immobilized on the cell surface. Ca2+ flux through endocytosed isotypes was correspondingly either significantly reduced or ablated in both subsets. In HCs, BCR endocytosis is clearly dependent on functional isotypes and IgL, and parallels events in normal B-cells. Lastly, we examined downstream effects of BCR signalling on cell viability, using soluble (sAb) and bound (bAb) anti-sIg antibodies. In a single IgD+ve mult-HCL case, both sAb and bAb anti-IgM yielded a significant level of apoptosis compared to control antibodies, whereas anti-IgD sAb resulted in no appreciable difference to level of spontaneous apoptosis, suggesting a disengagement of signals from this pathway. This disengagement was also observed in a separate HCL case expressing only IgD, and not in the mult-HCL cohort initially selected, where anti-IgD signals again did not increase levels of apoptosis. In IgD-ve mult-HCL (n=4), sAb and bAb specific cross-linking of IgG/A triggered significant apoptosis. These data demonstrate, for the first time, that mult-HCL retains a functional responsiveness via the BCR, suggesting an absence of anergic effects that may follow chronic antigen exposure in-vivo to self-antigen. Signals via sIgM/G/A isotypes, where functional, induce apoptosis in mult-HCL, whereas sIgD opposes such effects. Despite an apparently unique molecular mechanism of IgD expression in mult-HCL, this isotype appears to be hardwired in B-cells to mediate responses that differ from IgM. The persistent flux observed here indicates a more sustained and robust IgD signaling cascade, as also observed in B-cell models. These data reveal distinctive and opposing effects of individual isotypes on BCR mediated behavior in mult-HCL. While apoptotic responses appear to negate a role for antigen in tumor drive in-vivo, potential antigen engagement via IgD, if dominant leaves this question open. Disclosures: No relevant conflicts of interest to declare.

Description: Introduction Many patients are on long-term vitamin K antagonists (VKA) for atrial fibrillation (AF) or recurrent venous thromboembolism (VTE). This therapy proved highly effective for the prevention of stroke and recurrence of venous thrombosis. However, due to intra-individual variations in the dose-response relationship it can be difficult to keep the International Normalized Ratio (INR) within the therapeutic range. As underanticoagulation increases the thrombotic risk and overanticoagulation the bleeding risk, the efficacy and safety of VKA depend on the individual time in the therapeutic range (iTTR). Although patients on stable VKA therapy tend to stay stable over time, a proportion develops extreme overanticoagulation. It is well known that the iTTR is lowered directly after overanticoagulation. However, it is unclear whether such patients will subsequently restabilize. For that reason, we analyzed in a large cohort of AF and VTE patients the course of VKA therapy during the 3 months after extreme overanticoagualation. Material and Methods We selected from a consecutive cohort of 15,912 AF and VTE patients all patients who were on ‘stable VKA therapy’ during the 3 months ‘screening period’. The screening period started for the individual patient at the first INR between January 2009 and January 2012 that was measured ≥3 month after treatment initiation. Stable VKA therapy was defined by a maximum interval of 56 days between INR-measurements and the absence of extreme overanticoagulation (INR≥ 8.0 or unscheduled supplementation of vitamin K). End of follow-up was June 2012. In patients with extreme overanticoagulation (EO), we compared the 3 months before with the 3 months after EO. Patients with EO were also compared with the total group of selected patients. The primary outcome was inadequate iTTR (iTTR