Shanafelt, Tait D.

Abstract Abstract 2902 Background: Although chronic lymphocytic leukemia (CLL) is a low grade B-cell malignancy, 2–8% of patients (pts) are reported to undergo transformation to diffuse large B-cell lymphoma (DLBCL; Richter's syndrome [RS]). Whether the risk of transformation is related to the underlying biology of CLL or is a consequence of treatment for CLL is uncertain. Also, the role of prognostic markers such as immunoglobulin heavy chain (IGHV) gene mutation status, ZAP-70 and CD38 expression, and genetic abnormalities detected by fluorescence in situ hybridization (FISH) in predicting the development of RS is not well defined. The available data on stem cell transplant (SCT) in pts with RS is based on retrospective case series of selected RS pts and is of uncertain relevance to the majority of CLL pts experiencing RS. Therefore, we conducted a cohort study of newly diagnosed CLL pts to explore the incidence and natural history of RS. Methods: The Mayo Clinic CLL database includes all consenting pts with a pathologic diagnosis of CLL. Information on date of diagnosis, treatment history, and disease-related complications is abstracted from clinical records on all pts and then maintained prospectively. We used this database to identify newly diagnosed pts with CLL from January 2000 through July 2011, who were seen at our institution within 12 months of diagnosis. Pts with biopsy-confirmed RS were included in this analysis. For pts referred from an outside institution, pathology review at Mayo Clinic was mandatory to be included in this study. The Mayo Clinic Institutional Review Board approved the study. Results: Between January 2000 and July 2011, 1641 pts with newly diagnosed CLL were seen at Mayo Clinic within 12 months of diagnosis, and this cohort had a median follow-up of 4.0 yrs (range, 0–12.3 yrs). Of these pts, 37 (2.3%) were diagnosed with RS. The median time to development of RS after a diagnosis of CLL was 1.8 yrs (range, 0–11.7 yrs). The incidence of RS at 2 and 5 yrs post CLL diagnosis were 1.3% and 2.1% respectively (Figure). Pts who developed RS had more advanced (Rai III/IV) stage disease (22% vs. 6%; p<0.001) and higher beta 2-microglobulin levels (median 3.1 mg/dL vs. 2.3 mg/dL; p=0.003) at diagnosis of their CLL compared to pts without RS. Pts who developed RS were also more likely to be positive for ZAP-70 (58% vs. 33%; p=0.03), CD49d (77% vs. 31%; p=0.0004), and CD38 (57% vs. 29%; p=0.001), have unmutated IGHV (76% vs. 44%; p=0.003) and have either del(11q22.3) or del(17p13) on FISH analysis (46% vs. 13%; p<0.0001). RS transformation occurred prior to treatment of CLL in 17 (46%) pts and after treatment of CLL in 20 pts (54%). Treatment for CLL was associated with an increased risk of RS (92% vs 34%; p<0.0001). The odds ratio (OR) of RS was increased for pts who received purine nucleoside analogues (OR=3.0; 95%CI=[1.6, 5.9]; p=0.001), alkylating agents (OR=2.5; 95% CI=[1.3, 4.9]; p=0.004), or both (OR=3.3; 95% CI=[1.7, 6.4]; p=0.0003) for treatment of their CLL. Median overall survival after development of RS was 2.1 yrs. Most pts (29/37, 78%) received R-CHOP (rituximab, cyclophosphamide, doxorubicin, vincristine and prednisone) therapy. Two (5%) pts underwent an autologous SCT and 5 (14%) underwent an allogeneic SCT. Additionally, 1 (3%) patient received an autologous SCT followed by an allogeneic SCT. By the end of the study period, 17 (46%) pts with RS had died. Conclusion: The overall rate of biopsy-proven RS in this large cohort of pts with newly diagnosed CLL was 2.3% (5 year incidence: 2.1%). Clinical characteristics (Rai stage III/IV) and biologic characteristics of the CLL B-cell (positive expression of ZAP-70, CD38 and CD49d; unmutated IGHV; and either del(11q22.3) or del(17p13) on FISH) at the time of diagnosis were associated with future risk of RS. Exposure to purine nucleoside analogues and/or alkylating agents for treatment of CLL was also associated with increased risk of RS. Disclosures: Zent: GlaxoSmithKline: Research Funding; Novartis: Research Funding; Genentech: Research Funding; Genzyme: Research Funding; Biothera: Research Funding. Shanafelt:Genentech: Research Funding; Glaxo-Smith-Kline: Research Funding; Cephalon: Research Funding; Hospira: Research Funding; Celgene: Research Funding; Polyphenon E International: Research Funding.

Abstract BACKGROUND: Chronic lymphocytic leukemia (CLL) remains a heterogeneous disease despite significant advances in disease classification based upon cellular and molecular markers. Rai stage, immunoglobulin heavy chain variable region mutation status (IGHV), cytogenetic abnormalities, beta 2 microglobulin levels, expression of ZAP-70, CD38 and CD49d provide useful guides alone or in prognostic models for progression risk assessment but variability in clinical outcome in early Rai stage (Rai 0/I) unmutated (UM) IGHV patients persists. This variability in clinical outcome suggests that there are yet-to-be defined biologic/genetic factors that contribute to disease heterogeneity. Long non-coding RNAs (lncRNAs) display a range of diverse activities including regulation of gene transcription, post translational regulation and epigenetic regulation and represent an intriguing prospect for influencing CLL disease progression. LncRNAs have been implicated in diagnosis, prognosis and therapy of various cancers however their role in influencing disease progression in early Rai stage UM CLL has not yet been studied. Methods: To investigate a role for lncRNAs in UM Rai 0/I CLL patients we employed the Arraystar Human lncRNA Microarray v4.0. Using blood samples collected within 3 months of diagnosis, two cohorts of UM Rai 0/I patients were compared: one defined as progressive disease with time to first treatment (TTT) ≤ 2 years after diagnosis (n=34) and one as indolent disease with TTT ≥5 years after diagnosis (n=29). Differentially expressed lncRNAs were identified using Agilent GeneSpring GX Software v12.1. To be considered for further analysis, the difference in lncRNA expression had to have a fold change (FC) ≥ 2.0, a t-test p-value ≤ 0.05 and a false discovery rate (FDR) ≤ 0.05. Results: Over 1100 lncRNAs were found to be differentially expressed between the progressive and indolent UM CLL cohorts. Greater than 150 of these lncRNAs have known associated genes and are well annotated and validated. Among the differentially expressed lncRNAs, several are of particular interest and potentially relevant to CLL disease biology. For example, the lncRNA AL833181 was overexpressed in the progressive group. The associated gene for AL833181 is BCL11A and encodes a zinc finger protein that interacts with BCL6 and may itself serve as a proto-oncogene. Translocations involving BCL11A have been shown to identify a very aggressive subset of CLL (Am J Pathology, 2009). Therefore it is possible this lncRNA may be playing a role in deregulated expression of BCL11A. Within the indolent disease group, CTD-2566J3.1 was overexpressed >10-fold as compared to the progressive disease group. Its associated gene RAD51B is essential for DNA repair, suggesting the possibility that CTD-2566J3 may protect CLL cells from further DNA damage and disease progression. Also overexpressed in the indolent disease group were 2 lncRNAs that are associated with genes that encode proteins involved in the ubiquitin-proteasome system. USP2-AS1 lncRNA is associated with the USP2 gene and encodes an ubiquitin-specific protease required for TNF-alpha induced NF-kB signaling and is a specific deubiquitinase for cyclin D1, a known proto-oncogene. Furthermore, USP2-AS1 may also be linked to MYC. RP11-522I20.3 is associated with the QBLN1gene which encodes a protein that mediates the proteasomal degradation of misfolded or accumulated proteins. Thus, the associated lncRNAs may be acting as post-transcriptional gene silencers. Although CLL is not viewed as an "invasive" cancer, there were 5 lncRNAs overexpressed in the indolent group that are associated with Ankyrin genes which play a role in cell motility, activation and proliferation along with the lncRNA RP11-477D19 that is associated with theTIAM2 gene. TIAM2is a Rac guanine nucleotide exchange factor that can promote invasion and motility of cells. The respective lncRNAs may be down-regulating these genes and prohibiting malignant cell expansion. Conclusions: Our study reveals that there are indeed specific lncRNAs that are expressed at different levels in progressive versus indolent early Rai stage UM CLL and have the potential to impact a number of relevant biological processes and pathways. While these data are preliminary, the lncRNA AL833181 and its associated gene BCL11A may prove to be a potential marker and therapeutic target for aggressive disease. Disclosures Shanafelt: Pharmacyclics: Research Funding; Celgene: Research Funding; Cephalon: Research Funding; GlaxoSmithkKine: Research Funding; Genentech: Research Funding; Janssen: Research Funding; Hospira: Research Funding.

Abstract Background: CLL patients (pts) treated with novel targeted therapies continue to experience disease progression. Approximately 7-15% of relapsed CLL treated with ibrutinib or venetoclax developed Richter's syndrome (RS), an aggressive high grade lymphoma transformation. Standard chemotherapy has limited efficacy in RS. We hypothesized that checkpoint blockade would re-establish anti-tumor immune response in progressive CLL/RS and here we aim to update the clinical data and correlative analysis of MC1485: a phase 2 study of PD-1 blocking antibody pembrolizumab in relapsed/refractory CLL and RS. Methods: Relapsed/refractory CLL including RS enrolled in the CLL arm of MC1485 trial was reported here. The primary end point of this study is overall response rate (ORR). Pts with prior allogeneic stem cell transplant were excluded. Pembrolizumab 200 mg was administered intravenously every 3 weeks. NCI CTCAE v4.0 and IWCLL 2008 criteria were used for non-hematological adverse events (AE) and for CLL grade hematological AE. Tumor expression of PD-1 and PD-L1 were assessed with standard immunohistochemical (IHC) staining. Percentage expressions of individual antigens were analyzed with whole-slide scanning followed by image analysis with Image-Pro software (Media Cybernetics). Fluorescence in situ hybridization (FISH) was performed on available CLL/RS tissue sections to assess copy number of chromosome 9p region that contains PD-L1 and PD-L2. Results: 25 pts including 16 CLL and 9 RS (biopsy-proven large cell lymphoma) were enrolled in CLL arm. The median age was 69 years (46-81). Twelve (48%) pts had del(17p) or monosomy 17 or TP53 mutation. The median number of prior therapies was 4 (1-10). 96%, 72% or 48% of pts had received alkylator and anti-CD20 antibody, purine analog or anthracycline. Fifteen (60%) pts had prior ibrutinib and 12 (48%) progressed clinically while receiving ibrutinib, including 6 who progressed to RS and 6 who developed progressive CLL. The median number of pembrolizumab doses that pts received was 3 (1 to 21), administered over a median treatment duration of 11 weeks (1 to 56). Drug-related AE occurred in 21 pts (88%) with the most common ones being neutropenia in 9 (37%), cough in 7 (29%) and dyspnea in 6 (25%) pts. Drug-related grade 3 or above AE occurred in 9 (38%) pts with most common ones being thrombocytopenia (5, 21%), dyspnea (2, 8%), and fatigue (2, 8%). The most common immune-related AE was liver enzyme elevation (12%, 8% G3) and was reversible with therapy interruption or steroid therapy. Based on investigator assessment using the Revised Response Criteria for Lymphomas and IWCLL 2008 criteria, one RS pt had complete response (CR, 4%), 3 RS had partial responses (PR, 12%). Among 9 RS pts, 1 CR (11%), 3 PR (33%), 3 SD (33%) and 2 PD (22%) were observed. Thus the ORR in RS was 44%. No CLL pts achieved a CR/PR, 3 had SD and 9 had progressive disease (PD). The ORR of all pts was 16%. Of the 4 RS who had CR/PR, responses occurred early after 2 cycles of therapy and median duration of therapy for CR/PR pts was 8.3 months with data cut-off by June 30th 2016 (Figure 1A). The causes for therapy discontinuation in RS were PD (3, 33%), alternate therapy (2, 22%), and thrombocytopenia due to increased marrow CLL (1, 11%). Increased marrow CLL was observed in 2 RS pts with PR to RS phase of disease assessed by PET, thus the protocol was amended to allow addition of idelalisib/ibrutinib to control the underlying marrow CLL. For RS pts who had a CR/PR or SD, variable nodal responses were observed (Figure 1B). In particular, 6 RS who had prior ibrutinib experienced CR or PR or SD with nodal responses. After a median follow-up of 10.2 (1.9 to 16.1) months, the median overall survival (OS) for all pts was 10.7 months (95% confidence interval [CI], 5.4 to not reached). The 6 month OS rate for RS and CLL pts were 73% and 59%, respectively. Biomarker assessment using IHC analysis on 10 pts with available tumor/nodal tissues (6 RS and 4 CLL) showed an increased expression of PD-L1 (p = 0.02) and a trend for an increased expression of PD-1 (p = 0.1) in the group of pts with CR/ PR versus pts in the group with no clinical response. One out of 10 tested showed polysomic for chromosome 9p. Conclusion: Pembrolizumab had an acceptable safety profile in CLL and RS patients. We confirmed that pembrolizumab has substantial therapeutic activity in RS. Single-agent pembrolizumab does not appear to have clear activity in CLL. Disclosures Ding: Merck: Research Funding. Parikh:Pharmacyclics: Honoraria, Research Funding. Shanafelt:GlaxoSmithKline: Research Funding; Genentech: Research Funding; Janssen: Research Funding; Pharmacyclics: Research Funding; Celgene: Research Funding; Cephalon: Research Funding; Hospira: Research Funding.

Abstract Abstract 2893 Introduction: Monoclonal B-Cell Lymphocytosis (MBL) is a common asymptomatic condition characterized by a clonal B-cell population detected in the blood or bone marrow. The prevalence of MBL is approximately 3–5% in adults over age 40 but rises with age. MBL is a precursor state to CLL and other types of indolent non-Hodgkin lymphoma (NHL). Only a small subset of patients with MBL comes to clinical attention, typically during evaluation for low grade lymphocytosis (designated now as clinical MBL). The rate of progression to CLL requiring treatment among individuals with clinical MBL is ∼1%/yr, and the vast majority of patients with MBL will never develop a B-cell malignancy. Recent data indicate that individuals with MBL are at increased risk of infection similar to CLL. It is unknown whether individuals with MBL are at risk for other adverse outcomes associated with CLL, such as increased risk of non-hematologic cancers (NHC). We investigated the incidence of NHC among patients with clinical MBL and compared this to a cohort of general medicine patients and a cohort of CLL patients. Methods: Mayo Clinic Rochester (MCR) is the primary center for hematologic care in a region including southeastern Minnesota, northern Iowa, and western Wisconsin. No other hematology specialty centers are available within a 50 mile radius of MCR. To explore the risk of NHC in a local, community dwelling cohort of individuals with clinically-identified, CLL-phenotype MBL, we used the MCR CLL database to identify all individuals with newly diagnosed MBL seen in the MCR Hematology Division between January 1, 1999 and December 31, 2009. Analysis was limited to 154 MBL cases residing within 50 miles of MCR. The comparison cohort consisted of 596 adult general medicine patients, with no prior cancer, residing within 50 miles of MCR, who were seen for a general medical exam and enrolled as controls in a case-control study for NHL between April 25, 2004 and December 31, 2009. Rates of NHC in the MBL cohort were also compared to a cohort of 174 patients with newly diagnosed CLL seen in the same time interval as the MBL cohort and also living within 50 miles of MCR. NHC were identified using the Mayo Clinic Cancer Tumor Registry as well as review of medical records in all 3 cohorts. Patients with a NHC diagnosis >3 months prior to the diagnosis date of MBL/CLL were excluded from analysis while those with MBL/CLL and a NHC within 3 months of one another were considered to have a concurrent diagnosis. Results: There were 125 patients in the MBL cohort, 153 in the CLL cohort, and 596 in the control cohort after excluding patients with prior cancers. The MBL and CLL patients tended to be older (median age MBL=69, CLL=68, Control=58; p<0.0001) and more likely to be male (% male MBL=61, CLL=67, Control=46; p<0.0001) than the controls. After a median follow-up of 4.2 years (range 0–11), 20 (16%) individuals with MBL developed NHC as compared to 22 (4%) of the controls (Hazard Ratio (HR) MBL relative to control=5.0; 95% confidence interval (CI)=(2.6, 9.4; p<0.0001). Twenty CLL patients (13%) developed NHC, supporting a similar rate to that of MBL patients (HR MBL relative to CLL=1.3; 95% CI=(0.6, 2.5; p=0.49;See Figure). Specifically, the MBL cohort had a higher incidence of cancer of the breast, lung, and nervous system than that of the control cohort. The higher risk of NHC among individuals with CLL and MBL persisted even when patients with “concurrent diagnosis” of CLL/MBL and NHC were excluded (p=0.006) and when patients treated for progressive CLL were censored at the date of treatment (p=0.001) Finally, we performed a pooled multivariable analysis of all patients (n=874) adjusting for age, sex, major co-morbidities, presence of MBL, and diagnosis of CLL. Age (HR each year older=1.03; 95% CI 1.01–1.06; p=0.003), major comorbidities (HR=1.81; 95% CI 1.07–3.00; p=0.02), CLL (HR=2.10; 95% CI 1.01–4.01; p=0.04), and MBL (2.47; 95% CI 1.30–4.69; p=0.02) were independent risk factors for NHC. The results were similar when the effects of age was modeled in a non-linear (e.g. logarithmic) manner. Conclusions: In this cohort study, patients with newly diagnosed clinical MBL had a 2.5-fold increased risk of developing NHC relative to the control cohort. MBL was an independent risk factor for development of NHC after adjusting for age, sex, and other comorbidities. This finding adds to the growing evidence that clinical MBL has a distinct clinical phenotype. Disclosures: Shanafelt: Genentech: Research Funding; Glaxo-Smith-Kline: Research Funding; Cephalon: Research Funding; Hospira: Research Funding; Celgene: Research Funding; Polyphenon E International: Research Funding.

Abstract INTRODUCTION: Among patients (pts) with chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL), the indications for liver biopsy are not known. Additionally, the histopathologic findings of CLL infiltration in the liver along with its clinical implications have not been thoroughly described in the literature. METHODS: We identified all pts with a diagnosis of CLL/SLL from the CLL Clinical Database at Mayo Clinic, Rochester, MN who underwent a liver biopsy. We also cross referenced the Mayo Clinic Hematopathology Database for all pts who underwent a liver biopsy. The indications for biopsy, description of the pathologic findings in the liver biopsy, CLL therapy and outcomes were abstracted from the clinical records. Retrospective pathology review was performed on cases with CLL involvement in which slides were available for review. RESULTS: Fifty-two CLL/SLL pts who underwent a liver biopsy were identified. The indications for liver biopsy were as follows: liver lesion identified on radiographic imaging in 21 (41%) pts, abnormal liver function tests (LFTs) in 17 (33%) pts, hepatosplenomegaly in 11 (21%) pts, and unknown in 3 (6%) pts. Among all 52 pts, there was concern for Richter transformation at time of biopsy in 7 (13%) pts. Types of biopsy were as follows: percutaneous in 20 (39%) pts, intraoperative in 17 (33%) pts, transjugular in 3 (6%) pts, and unknown in 12 (23%) pts. CLL/SLL involvement was identified in 38/52 (73%) pts undergoing liver biopsy. Among these, the diagnosis of CLL/SLL was made on liver biopsy in 8 pts, and 7 pts had additional findings on their liver biopsy including metastatic colon cancer (n=3), hemochromatosis (n=2), steatohepatitis (n=1), and cirrhosis (n=1). Liver biopsy revealed Richter transformation in 4 (8%) pts (3 pts with diffuse large B cell lymphoma (DLBCL) and 1 patient with Hodgkin lymphoma), other malignancy in the absence of CLL in 7 (15%) pts (2 metastatic colorectal, 2 metastatic esophageal, 1 hepatocellular carcinoma, 1 metastatic lung, and 1 neuroendocrine), and 1 patient with steatohepatitis. Two (4%) pts had normal findings on liver biopsy. Among the 38 pts with liver involvement by CLL, 27 had slides available for retrospective pathology review. CLL involvement ranged from 2-100% of the liver parenchyma. Seven pts (26%) underwent excisional biopsies or resections and 20 (74%) underwent core biopsies. The portal tracts were the most common region of the liver involved (22/26 pts, 85%). Of these, 8/22 (36%) pts had extension into the lobules or sinusoids, as well. Of the 4 cases without portal involvement, 2 showed extensive involvement such that it effaced the liver parenchyma in the region of involvement. One patient (4%) had a predominantly sinusoidal involvement. One patient (4%) showed small nodular infiltrates that were difficult to localize due to their size. Proliferation centers were noted in only 3 pts (11%). Most pts (29/38; 76%) whose liver biopsy demonstrated involvement by CLL did not receive immediate CLL-specific treatment. Nine of the 38 pts (24%) with CLL involvement on liver biopsy received therapy (Table): purine analog based therapy (n=4), rituximab and steroids (n=2), steroids only (n=1), alkylator and rituximab (n=1), and ibrutinib (n=1). Pts with extensive involvement of the liver by CLL were more likely to receive purine nucleoside analog based therapy compared to pts with portal infiltration by CLL (2/2 pts [100%] vs. 1/6 pts [17%]). The remaining pts were offered no therapy due to incidental finding of CLL in the liver biopsy (n=11), chemotherapy for other cancer (n=5), palliative care (n=3), or unknown (n=10). Pts with Richter's transformation received R-CHOP (n=2) and CHOP (n=1) for DLBCL, and ABVD (n=1) for Hodgkin lymphoma. Pts with other cancers without CLL received appropriate therapy for their underlying malignancy. CONCLUSION: Abnormal LFTs and radiographic abnormalities were the most common indications for a biopsy in this large cohort of CLL pts. Infiltration of the portal tracts by CLL/SLL was the most common histopathological finding. Proliferation centers were not commonly seen, which may make the diagnosis challenging for the pathologist if there is not a prior history of CLL/SLL. The mere presence of CLL/SLL infiltration did not mandate treatment and many pts were able to continue observation. Table Table. Disclosures Ding: Merck: Research Funding. Kenderian:Novartis: Patents & Royalties, Research Funding. Shanafelt:GlaxoSmithkKine: Research Funding; Celgene: Research Funding; Cephalon: Research Funding; Genentech: Research Funding; Janssen: Research Funding; Pharmacyclics: Research Funding; Hospira: Research Funding. Parikh:Pharmacyclics: Honoraria, Research Funding.

Abstract Background. Trisomy 12 (tris12) is a recurrent cytogenetic abnormality in chronic lymphocytic leukemia (CLL), occurring in approximately 15-20% of cases, often as the unique cytogenetic alteration, that is usually considered a clonal driver lesion occurring early in CLL evolution. In the Dohner hierarchical categorization, tris12 CLL are identified as having an intermediate prognostic risk, although recent reports suggest a more complex and heterogeneous clinical behavior. Compared to CLL lacking this cytogenetic abnormality, tris12 CLL show more atypical morphology and immunophenotype, more frequent expression of the negative prognostic markers CD49d and CD38, and presence of NOTCH1 mutations and an unmutated (UM) IGHV gene status. The increased fraction of tris12 CLL carrying adverse prognostic features is in contrast to the intermediate clinical behavior associated with most tris12 CLL cases. Aim. To perform a comprehensive evaluation of the clinical impact of the major genetic, immunogenetic and immunophenotypic prognostic markers in tris12 CLL. Methods. The study was based on a multicenter series of tris12 CLL defined according to Dohner (n=283, including 73 cases also bearing del13q), and a comparison group (control) of 553 cases with either del13q (n=308) or without any cytogenetic abnormality (no del17p, del11q, tris12, del13q, n=245). Median follow-up of patients in the tris12 and control groups were 4 years (range 0-22) and 7 years (range 0-28), with 54% and 57% treated patients, and 18% and 15% deaths, respectively. Patient characterization included modified Rai stage, CD49d (CD49dhigh, ≥30% positive cells by flow cytometry), CD38 (CD38high, ≥30% positive cells by flow cytometry) and ZAP-70 (ZAP-70high, ≥20% positive cells by flow cytometry) expression, and IGHV mutational status (mutated, M, or UM according to the 2% cutoff). TP53, BIRC3, NOTCH1 andSF3B1 mutations were screened either at diagnosis or before therapy by NGS with at least 1000X coverage and 1% of sensitivity. Groups were compared by chi-square test; overall survival (OS) was computed from diagnosis to death or censored at last observation, and analyzed by Cox regression analysis. Results. Comparing the tris12 and the control groups, median age was 64 years (range 30-92) vs 66 years (range 33-92), male gender 55% vs 56% (p=0.86), the modified Rai stage was early in 52% vs 54%, intermediate in 41% vs 42% and advanced in 7% vs 4% (p=0.20). As previously reported, tris12 CLL were characterized by a higher prevalence of cases expressing CD49d (85% vs 31%) and CD38 (62% vs 17%; all p<0.0001), and of UM IGHV cases (55% vs 25%, p<0.0001). Analysis of recurrent mutations highlighted a higher prevalence of NOTCH1 mutations (26% vs 8%, p<0.0001) and of BIRC3 mutations (21% vs 1%, p<0.0001) in tris12 vs control group CLL. Conversely, no differences were found in the fraction of cases with TP53 mutations (3% vs 4%, p=0.38) or SF3B1 mutations (7% vs 7%, p=0.89), and in cases expressing ZAP-70 (62% vs 52%, p=0.09). The impact of these features on OS was tested by univariate analysis: in tris12 CLL, only the UM IGHV gene status predicted shorter OS (HR=2.37, p=0.0063), while none of the other characteristics reaching statistical significance as OS predictors (CD49d HR=1.36, p=0.36; CD38 HR=0.42, p=0.052; ZAP-70 HR=3.12, p=0.07; TP53 HR=2.33, p=0.25; NOTCH1 HR=1.40, p=0.22; SF3B1 HR=2.05, p=0.17; BIRC3 HR=1.22, p=0.61). On the other hand, in the control cohort, a significantly higher HR was found for CD49d (HR 3.11, p<0.0001) and CD38 (HR 3.45, p<0.0001) expression, TP53 (HR 2.88, p=0.0026), NOTCH1 (HR 3.57, p<0.0001), and SF3B1 (HR 2.57, p=0.0038) mutations, as well as for the UM IGHV gene status (HR=2.81, p<0.0001), but not for ZAP-70 expression and BIRC3 mutations (HR=1.74 and HR=1.91, p=0.15 and p=0.37, respectively). Conclusions. Mutational status of IGHV genes was the sole prognostic factor able to stratify OS in tris12 CLL. Despite the high frequency of NOTCH1 and BIRC3 mutations, as well as of CD49d and CD38 overexpression, these markers failed to convey a prognostic risk in tris12 CLL. The lack of a significant clinical impact for TP53 and SF3B1 mutations might be partly explained by the low number of mutated cases combined with a relative short follow up in our tris12 cohort. These findings are in keeping with the hypothesis of a different patho-biological mechanism occurring in tris12 CLL, which however remains to be fully elucidated. Disclosures D'Arena: Janssen-Cilag: Honoraria. Rossi:Gilead: Honoraria, Research Funding; Abbvie: Honoraria; Janseen: Honoraria. Gaidano:Janssen: Consultancy, Honoraria, Speakers Bureau; Gilead: Consultancy, Honoraria, Speakers Bureau; Novartis: Consultancy, Honoraria, Speakers Bureau; Roche: Consultancy, Honoraria, Speakers Bureau; Morphosys: Consultancy, Honoraria; Karyopharm: Consultancy, Honoraria. Shanafelt:Genentech: Research Funding; Janssen: Research Funding; Celgene: Research Funding; GlaxoSmithkKine: Research Funding; Pharmacyclics: Research Funding; Cephalon: Research Funding; Hospira: Research Funding.

Abstract Background: Individuals with clinically ascertained monoclonal B-cell lymphocytosis (c-MBL) having the phenotype of the chronic lymphocytic leukemia (CLL) have a 1-4% per year risk of progression to CLL requiring therapy. The risk factors for progression and the outcomes of individuals with c-MBL are not well defined. Methods: Using the Mayo Clinic CLL Database, we identified individuals with c-MBL (absolute B-cell count of <5x109/L, in the absence of symptoms, organomegaly, splenomegaly and cytopenias) who were seen at Mayo Clinic, Rochester, MN between 01/1995 - 5/2016. Patients in whom an absolute B-cell count was not available were included in the analysis if the absolute lymphocyte count was <5x109/L. Baseline clinical characteristics and prognostic test results (including IGHV mutation status, genetic abnormalities detected by FISH, and expression of ZAP-70, CD38 and CD49d) were recorded. Time to first therapy (TFT) was analyzed using cumulative incidence methods accounting for competing risk of death. Multivariable Cox proportional hazards regression analysis was used to identify factors that predicted TFT. Because of missing data for some prognostic parameters, multiple models were run, introducing one novel prognostic factor at a time to the base model (which consisted of age and sex). Overall survival (OS) of these individuals was compared to age- and sex-matched population of the state of Minnesota. Results: Eight hundred and fifty-one individuals with c-MBL were identified and included in this analysis. Median age was 69 years (range, 38-95 years), and 527 (62%) were males. The median absolute B-cell count at the time of diagnosis was 2.6 x 109/L (range, 0.1-5.0 x 109/L). The median serum beta-2 microglobulin (β2M) was 2.2 mg/dL (range, 1.0 - 21.5 mg/dL). One hundred and nine (30%) individuals had unmutated IGHV genes, and 38 (7%) had high-risk FISH (defined as either del17p13 or del11q23). The CD38 (≥30%), ZAP-70 (≥20%), and CD49d (≥30%) status was positive in 19%, 23% and 34% individuals, respectively. After a median follow-up of 6.8 years, 99 individuals required therapy for progressive disease (at a rate of 2.1% per year, Figure 1). On multivariable analysis, the following factors were associated with a higher risk of progression to CLL requiring therapy: a) unmutated IGHV status (hazard ratio [HR]:3.8, 95%CI 2.1 - 7.0, p<0.0001); b) positive CD49d status (HR: 3.1, 95%CI 1.6 - 5.9, p=0.0006); and c) positive CD38 status (HR: 2.8, 95% CI 1.7 - 4.8, p<0.0001). Although the HR for high-risk FISH was 2.0 (95% CI 0.9 - 4.4), it was not significantly associated with TFT (p=0.11), likely due to small sample size. Age, sex, serum β2M, and ZAP-70 expression were not predictive of TFT. Among these individuals with B-cell counts <5x109/L, further stratification of the absolute B-cell count at diagnosis showed no association with TFT (Figure 2). The median OS of individuals with c-MBL was 11.8 years. Although the OS among individuals with c-MBL and the age- and sex-matched general population of Minnesota appeared similar for the first 10 years of follow-up, OS was significantly shorter in the c-MBL group during the full follow-up interval (p=0.004, Figure 3). Conclusion: In this large cohort of individuals with clinically ascertained MBL, the risk of progression to CLL requiring therapy was 2.1% per year. Biological characteristics of the B-cell clone including IGHV mutation status, and CD49d and CD38 status predicted time to first CLL therapy. On extended follow-up, the OS of individuals with c-MBL was significantly shorter relative to age- and sex-matched general population. These findings have important implications for counselling individuals with clinically ascertained MBL. Disclosures Parikh: Pharmacyclics: Honoraria, Research Funding. Ding:Merck: Research Funding. Kenderian:Novartis: Patents & Royalties, Research Funding. Shanafelt:Pharmacyclics: Research Funding; GlaxoSmithkKine: Research Funding; Janssen: Research Funding; Genentech: Research Funding; Celgene: Research Funding; Cephalon: Research Funding; Hospira: Research Funding.

Abstract Abstract 2901 Background: The median age at diagnosis of patients (pts) with chronic lymphocytic leukemia (CLL) is 72 years (yrs). According to the Surveillance and Epidemiology End Results (SEER) database, approximately 11% of all pts diagnosed with CLL in 2009 were <55 yrs. All previously reported series on the natural history of younger CLL pts are more than a decade old, and did not include information on contemporary prognostic parameters (such as immunoglobulin heavy chain gene mutation status [IGHV], genetic abnormalities by fluorescence in-situ hybridization [FISH], ZAP-70, etc). These reports also occurred prior to the introduction of modern treatment strategies (e.g. chemoimmunotherapy (CIT); reduced intensity allogenic stem cell transplant [SCT]), making their data on important clinical outcomes such as time to first treatment (TTT) and overall survival (OS) of uncertain relevance to younger pts in the modern era. Methods: We explored the natural history of younger pts with CLL using the Mayo Clinic Database. All pts ≤ 55 with pathologic diagnosis of CLL who were seen at the Mayo Clinic between January 1995 and April 2012 were included in this study. Baseline demographic and clinical characteristics, prognostic variables and administered treatments were abstracted from the medical records. Outcomes of pts in this cohort was compared to CLL pts >55 seen during the same time period. OS of pts ≤55 was also compared to the age- and sex- matched normal population of the state of Minnesota. The Mayo Clinic Institutional Review Board approved this study. Results: Collectively, 844 pts ≤ 55 yrs (median age, 48.7 yrs) with newly diagnosed CLL and seen within 1 year of diagnosis were included in this analysis. The characteristics of these pts were compared to 2324 newly diagnosed pts>55 yrs (median age, 68.4 yrs) seen during the same interval. When compared to pts>55, younger pts were more likely to present as intermediate Rai stage disease (p<0.0001), IGHV unmutated (p=0.001), and ZAP-70 positive (p=0.009). Younger pts were also more likely to have 1 or more first degree relatives with CLL (familial CLL) than older pts (10.9% vs. 8.5%; p=0.04). No significant differences were seen in the gender distribution, CD38 status, or FISH risk category. When pts ≤ 55 were further stratified by age, 204 (24%) were ≤45 yrs, 272 (32%) were 46–50 yrs, and 368 (44%) age 51–55 yrs at diagnosis. Similar to the comparison with the >55 year old group, pts ≤45 were more likely to present with intermediate Rai stage disease (61.7%) than those 46–50 yrs (52.5%), or 51–55 yrs (48.8%; p<0.01). Pts ≤45 were also more likely to be IGHV unmutated (p=0.034) and ZAP-70 positive; however, the ZAP-70 status was not significantly different (p=0.095). No difference in the prevalence of familial CLL was observed by the age stratifications of the ≤55 group. After a median follow-up of 5.5 yrs (range, 0–17 yrs), 426 (50%) pts ≤55 had received treatment for CLL and 192 (23%) pts had died. Pts ≤55 had a shorter TTT (4.0 yrs vs. 5.2 yrs; p=0.001) but longer OS (12.5 yrs vs. 9.5 yrs; p<0.0001) compared to pts >55 yrs. In contrast, no differences in TTT or OS were observed when the age ≤55 pts were sub-stratified into the ≤45, 46–50, and 51–55 age groups. A significantly higher proportion of pts≤55 received SCT than those >55 (7% vs. 1%; p<0.0001), with even further stratification of the ≤55 group (SCT age≤45: 13.7%; age 46–50: 5.1%; age 51–55: 3.5%; p<0.0001). As a group, CLL pts ≤55 have significantly shorter OS than the age- and sex-matched population (median CLL=12.5 yrs; median population=not reached; p<0.0001, Figure). However, pts≤55 who were Rai Stage 0 and had mutated IGHV had comparable survival to the general population (p=0.97). Similarly, pts≤55 who were Rai Stage 0 and had favorable FISH results (13q- or normal) had comparable survival to the general population (p=0.27). Conclusion: Our study is the first comprehensive analysis of younger CLL pts in the modern era. We found that younger pts are more likely to present with intermediate Rai stage disease, and have IGHV unmutated and ZAP-70 positive status. Consistent with these characteristics, younger pts experience shorter TTT. Although the OS of younger CLL pts is longer than those >55, their survival relative to the age- and sex-matched normal population is profoundly shortened even with the advent of CIT and SCT. Disclosures: Shanafelt: Genentech: Research Funding; Glaxo-Smith-Kline: Research Funding; Cephalon: Research Funding; Hospira: Research Funding; Celgene: Research Funding; Polyphenon E International: Research Funding.

Abstract Introduction: The use of B-cell receptor (BCR) signal inhibitors-based therapies (e.g., Ibrutinib) for B-chronic lymphocytic leukemia (CLL) was initiated just a few years ago but has rapidly escalated due to their clinical efficacy and relative ease of use. However newer therapeutic approaches are needed due to multiple issues including the continued need to improve complete responses and reduce toxicity profiles. To that end our group has discovered a novel membrane target in the ubiquitous presence of Axl receptor tyrosine kinase (Axl RTK) on CLL B-cells and has reported that the Axl RTK inhibitor TP-0903 is able to induce apoptosis of CLL B-cells at nanomolar doses (Sinha, Clin Cancer Res, 2015). Given this we assessed if TP-0903 would be effective in the induction of apoptosis of leukemic B-cells from CLL patients who are currently on Ibrutinib therapy or whom have relapsed while on Ibrutinib treatment. Methods: Relapsed/refractory CLL patients (n=22) who were placed on Ibrutinib for progressive disease provided blood samples at a median of 3.2 months after Ibrutinib therapy initiation for these studies. We also obtained sequential samples on 8 patients from initial start of ibrutinib therapy and then over a 6 month follow-up period. CLL B-cells from these blood samples were subject to Ficoll separation, purified by using a Rosette Sep B-cell enrichment kit and then studied by flow cytometry to determine Axl RTK expression levels by flow cytometric analysis. Purified CLL B-cells (CD19+/CD5+) were cultured with TP-0903 in vitroat increasing doses (0.01µM - 0.50µM) for 24 hours and the LD50 dose was determined. In addition, 3 CLL patients who had been on Ibrutinib therapy and had a documented relapse were studied in similar fashion using TP-0903. LD50-sensitivity was measured. "LD50-sensitivity" was defined as an LD50 ≤0.50µM and "insensitive" was defined as an LD50 dose >0.50µM. CLL prognostic factors (e.g., FISH, IGHV mutation status, Rai stage, CD38, and CD49d) were evaluated at the time of ibrutinib treatment. Differences in factors between sensitive and insensitive cases were computed using the Kruskal-Wallis test for continuous variables and Chi-square test for categorical variables. Results: Twenty-two CLL patients (5 female, 17 male) were included in the analysis. Fourteen (64%) patients were found to be TP-0903 LD50-sensitive. Axl expression on CLL B-cells for this cohort was heterogeneous with a median of CD19+/CD5+ cells positive for Axl at 69.9% (range of 2.7-91.3%). The sensitive subjects tended to be younger with a median age at Ibrutinib treatment initiation of 62 vs 75.5 years (p=0.004). There were no significant differences in gender, FISH, IGHV mutation status, CD38, CD49d, or Rai stage between the sensitive and insensitive LD50 groups. There were no significant differences in relation to median Axl expression on CLL B-cells (sensitive: 72.6%, range: 2.7-91.3%; insensitive: 41.5%, range: 16.5-83.1%; p=0.35). The median number of treatments prior to initiation of ibrutinib did not differ between sensitivity groups (sensitive: 2.53, range: 8-10; insensitive: 43.5, range 12-20; p=0.2833). Association for ZAP70+ CLL B-cells tended to have more apoptosis induction by TP-0903 (sensitive: 84.6% ZAP70+; insensitive: 42.9% ZAP70+; p=0.052). In 8 CLL patients that were studied sequentially while on Ibrutinib continued to express Axl or increased their Axl expression (n=2) over a 3-6 month follow-up period. Three CLL patients who had relapsed on Ibrutinib were sensitive to TP-0903 with LD50 values of ≤0.50µM. Summary: Here we find that CLL B-cells from over 60% of relapsed CLL patients on Ibrutinib therapy were highly sensitive to the high-affinity Axl inhibitor TP-0903 with induction of apoptosis at nanomolar doses (≤0.50µM). The sensitivity of CLL B-cells to TP-0903 appears to be independent of Axl expression levels and of the known CLL prognostic factors but more evident for younger patients and for ZAP70+ expression status. Given this level of activity for apoptosis induction of CLL B-cells by TP-0903 encourages the further testing of this drug in clinical trials for CLL patients. Disclosures Parikh: Pharmacyclics: Honoraria, Research Funding. Shanafelt:Pharmacyclics: Research Funding; Janssen: Research Funding; Genentech: Research Funding; GlaxoSmithKline: Research Funding; Celgene: Research Funding; Cephalon: Research Funding; Hospira: Research Funding. Warner:Tolero Pharmaceuticals: Employment, Equity Ownership, Patents & Royalties. Bearss:Tolero Pharmaceuticals: Employment, Equity Ownership, Patents & Royalties. Kay:Pharmacyclics: Research Funding; Tolero Pharmaceuticals: Research Funding; Acerta: Research Funding; Gilead: Membership on an entity's Board of Directors or advisory committees; Morpho-Sys: Membership on an entity's Board of Directors or advisory committees; Infinity Pharm: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees.

Abstract BACKGROUND: Infiltration of the spleen plays an important role in the disease progression of patients with chronic lymphocytic leukemia (CLL). Despite this fact, the role for splenectomy in the management of CLL is not well defined. Historically, splenectomy has primarily been used for management of select patients with auto-immune cytopenias (e.g. autoimmune hemolytic anemia [AIHA], immune thrombocytopenic purpura [ITP]). We conducted a retrospective study to evaluate the utility of splenectomy in CLL patients cared for at Mayo Clinic over the last 20 years. METHODS: We used the Mayo Clinic database to identify all CLL patients who underwent splenectomy at Mayo Clinic since 1995. Medical records were reviewed to identify the indications for splenectomy, the pathologic findings at the time of surgery, and clinical outcomes. The indications for splenectomy were categorized as: diagnostic splenectomy, AIHA, ITP, symptomatic splenomegaly, and other. Pathology reports were reviewed to identify the findings at the time of surgery with respect to involvement by CLL and/or other lymphoproliferative disorders. RESULTS: Of the 5333 CLL patients seen at Mayo Clinic between 1/1/1995 and 12/31/2015, 107 (2%) underwent splenectomy at Mayo. The rate of splenectomy in female subjects was 1.7% (31/1779), and the rate in male subjects was 2.1% (76/3554). Of the 2354 subjects with IGHV mutation status, the rate of splenectomy in IGHV mutated subjects was 2.1% (23/1085) compared to 0.7% (9/1269) in IGHV unmutated subjects (p=0.004). The indication for splenectomy in these 107 patients was diagnostic splenectomy in 14 (13.1%) patients, ITP in 22 (20.6%), hemolytic anemia in 19 (17.8%), ITP and hemolytic anemia in 3 (2.8%), symptomatic splenomegaly in 46 (43.0%), and 3 (2.8%) other lymphomas. The rate of splenectomy decreased over the interval of the study (Figure). The per year risk of requiring splenectomy for patients diagnosed with CLL prior to 1995 was 0.32%/year, compared to 0.30%/year for those diagnosed from 1995-1999, 0.24%/year for those diagnosed from 2000-2004, 0.15%/year for those diagnosed from 2005-2009, and 0.16%/year for those diagnosed from 2010-2015 (p=0.01). The indication for splenectomy also changed over the study interval (Table) Pathologic review of the spleen demonstrated normal splenic tissue in 3 (2.8%), infiltration by CLL in 99 (92.5%), involvement by diffuse large B-cell lymphoma in 2 (1.9%) and involvement by other lymphomas in 3 (2.8%; T-cell lymphoma [n=1], T-cell large granular lymphocytic leukemia [n=1], and splenic marginal zone lymphoma [n=1]). CONCLUSION: These findings describe a large experience with the use of splenectomy in patients with CLL. Splenectomy is utilized relatively rarely (2% of CLL patients). The role of splenectomy in the management of CLL also appears to be changing with both a decreased frequency of splenectomy and a change in the indication for splenectomy over the last 2 decades. The potential benefits of splenectomy must be weighed against the know risks such as a lifelong increased risk of infection, as well as a higher risk of thromboembolism and secondary cancers. Splenectomy Indication by Time Period of CLL Diagnosis Table 1 Table 1. Figure 1 Figure 1. Disclosures Parikh: Pharmacyclics: Honoraria, Research Funding. Ding:Merck: Research Funding. Shanafelt:GlaxoSmithkKine: Research Funding; Janssen: Research Funding; Genentech: Research Funding; Pharmacyclics: Research Funding; Cephalon: Research Funding; Celgene: Research Funding; Hospira: Research Funding.