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Abstract Abstract 1546 Background: Follicular lymphoma (FL) is an incurable disease with an undefined optimal management strategy. Global priorities in goals of care are avoidance of death and transformation to aggressive subtypes. Retrospective series, – most including patients diagnosed before ubiquitous rituximab use, - describe diverse rates of transformation with a common consensus of 3% per year, and with a median survival post transformation of less than 2 years. This study sought to characterize transformation events in a prospective observational series begun after diffusion of early rituximab use in FL. Methods: Newly diagnosed FL patients were prospectively enrolled in the University of Iowa/Mayo Clinic SPORE Molecular Epidemiology Resource (MER) from 2002–2009. Clinical data were abstracted from medical records using a standard protocol. Patients were actively followed for retreatment, transformation, and death. Inclusion criteria for this analysis were initial diagnosis of grade I-IIIa FL. Exclusion criteria for this cohort include composite diffuse large B-cell lymphoma (DLBCL), FL grade IIIb, or evidence of clinical or pathological transformation at the time of FL diagnosis. Transformation was defined as refractory/recurrent disease with either a) biopsy confirmed subtype of FLIIIb, DLBCL or higher grade B-cell lymphoma; or b) clinical indication of transformation (sudden rise in LDH, rapid discordant localized nodal growth, new involvement of unusual extranodal sites, new B symptoms or hypercalcemia). Risk of transformation was analyzed via time to transformation using a death as a competing risk. Time to transformation was defined as the date of initial FL diagnosis to date of transformation. Overall survival was defined as the date of initial diagnosis to date of death or last known follow-up for patients still alive. Results: There were 631 newly diagnosed grade I-IIIa FL patients with a median age at enrollment of 60 years (range 23–93). 54% were male. The most common types of initial therapy were observation (33%), rituximab (R) monotherapy (12%), alkylator based chemotherapy +/− R (22%), and anthracycline based chemotherapy +/− R (20%). At a median follow-up of 60 months (range 11–110), 79 patients had died, 311 patients had an event (death, progression, or retreatment), and 60 patients (9.5%) had transformed. Transformation was biopsy proven in 48 of the 60 patients (80%). The overall transformation rate at 5 years (TX5) was 10.7% (95% CI: 8.3%–13.8%) (Figure 1). Time to transformation was associated with a FLIPI score of 3–5 (HR=2.37, 95% CI 1.28–4.39, p=0.006), but was not significantly associated with other standard clinical characteristics. Risk of transformation was different in the common initial treatment groups with the highest rate in patients who were initially observed (TX5=14.4%) and lowest rate in patients who initially received R monotherapy (TX5=3.2%)(p=0.058). Outcome after transformation was inferior to MER subjects with de-novo diagnosed DLBCL (p<0.0001). The median overall survival from date of transformation was 44 months (95% CI: 22-NA). Survival after transformation was superior in patients who transformed greater than 18 months after FL diagnosis compared to patients who transformed earlier (5 yr OS =70% vs 20%) (p=7 ×10−5), and for those initially observed (median unreached) versus those patients who were initially treated with alkylator or anthracycline based chemotherapy (median survival of 11 months)( p=0.016). Conclusions: Follicular transformation rates in this modern large prospective observational study are similar to risk of death without transformation and slightly lower at 5 years than most previous reports. Post-transformation prognosis is substantially better than described in older series. These observed differences may be a function of the prospective nature of the study design, modern management strategies, or patient selection factors. Initial management strategies may influence the risk of transformation. Marked survival differences following early vs. late transformation suggest that these may be different biologic events. Disclosures: Link: Genentech: Consultancy, Research Funding; Celgene: Consultancy; Millenium: Consultancy. Johnston:Novartis: Consultancy.

Abstract Background: Bruton’s tyrosine kinase (BTK) is an essential component of the B-cell receptor signaling pathway, a pathway critical to the survival and proliferation of malignant B cells. Ibrutinib, a small molecule inhibitor of BTK, has shown significant activity in several B-cell malignancies and is currently FDA approved for the treatment of patients (pts) with CLL or mantle cell lymphoma who have received at least one prior treatment.In a Phase 1 dose-escalation study, ibrutinib induced a response in 6 (38%) of 16 patients (pts) with relapsed/refractory FL and 6/11 (54%) of pts treated at doses ≥ 2.5 mg/kg (Advani JCO 2013, Fowler ASH abstr 156:2012). 560 mg daily was identified as a well-tolerated dose in lymphoma resulting in full-target occupancy. On the basis of these results, the Mayo Clinic and Princess Margaret P2Cs conducted a CTEP-sponsored Phase 2 trial of single-agent ibrutinib in relapsed/refractory FL (NCI 9271). Methods: Eligible pts had relapsed or refractory FL (Gr 1, 2, or 3a) that had progressed during or after 1 or more prior chemotherapy regimens. Therapy consisted of ibrutinib, 560 mg daily, until progression or unacceptable toxicity. Response was assessed by CT at 8 weeks and then every 12 weeks. All pts were required to have an on-study biopsy and a second biopsy at progression after response with fresh tissue collected for correlative studies. The primary endpoint was overall response rate (ORR) and secondary endpoints were safety and tolerability, overall survival, time to response, time to treatment failure, duration of response, and progression-free survival (PFS). Planned exploratory correlative studies included C1D8 and C3D1 FDG-PET response evaluation in a subset of 20 patients, and whole-transcriptome sequencing for correlation of mutations with response and resistance. Results: 40 patients (38 evaluable for response) were accrued from April 2013 to April 2014. Median age was 64 years (range 46-82), 70% were men, 55% had FLIPI ≥ 3, median number of prior regimens was 3 (range 1-11), 20% had a prior stem cell transplant, 45% were rituximab refractory, and 36% were refractory to their most recent treatment. At a median follow-up of 6.5 months (mo) (range 1.8-14.6+), the ORR for the 40 intention-to-treat pts is 30% (95% CI: 17-47%) with 1 CR and 11 PRs by CT criteria (4/12 responders had a negative restaging PET/CT). 26 (65%) patients have exhibited tumor size reduction. Only 2/18 (11%) pts with rituximab-refractory disease responded, compared to 8/19 (42%) pts with rituximab-sensitive disease (P=0.06) and 2/3 who were rituximab-naïve. There was no correlation between response and number of prior regimens. Median time to response was 2.4 mo (range 1.8-12.9 mo). Median PFS is 9.9 mo (95% CI: 6 mo, not reached). One of 12 responders has progressed after 9.9 mo on treatment. Median treatment duration was 5 mo (range 1-15+ mo). Dose delays (2 pts) and reductions were infrequent (4 pts). 17 pts have discontinued treatment due to PD (12), refusal (2), AEs (2), and death (1). Gr 3-4 AEs occurred in 30% of pts, including the following AEs in more than 1 pt: anemia (2), neutropenia (3), and infection (2). 3 pts have died (1 PD, 1 pneumonia, 1 gastric hemorrhage). Of the 20 pts with C1D8 PET scans, 19 also had C3D1 PET scans and were evaluable for response. Six of these 19 pts had objective responses by CT criteria at week 8 or beyond. Of the 6 responders, C1D8 PET/CT showed qualitative (visual) improvement in 3 pts, no visual change in 1 pt, and qualitative worsening in 2 pts. On the C3D1 PET/CT, 4 of 6 had qualitative improvement and 2 had no change. Evaluation of quantitative PET data including SUVs and total lesion glycolysis is ongoing and will be presented. Conclusions: Single agent ibrutinib is well tolerated with a modest ORR in relapsed/refractory FL at this early assessment. Continued follow-up is warranted to capture late responders and to establish response duration. Ibrutinib appears less active in FL than in MCL and CLL. Early PET scans (C1D8) do not reliably predict for response. Support by N01-CM-2011-00099 Disclosures Bartlett: Gilead: Consultancy, Research Funding; Seattle Genetics: Consultancy, Research Funding; Astra Zeneca: Research Funding; Janssen: Research Funding; ImaginAb: Research Funding; Genentech: Research Funding; Millennium: Research Funding; Pfizer: Research Funding; Pharmacyclics: Research Funding; Novartis: Research Funding; Medimmune: Research Funding; Celgene: Research Funding. Off Label Use: PF-05082566 for B-NHL. Kuruvilla:Janssen: Honoraria. Reeder:Millennium, Celgene, Novartis: Research Funding.

Abstract Abstract 2741 Background: The novel agent lenalidomide (LEN) has shown significant single-agent activity in patients with relapsed lymphoma through anti-proliferative and immunomodulatory mechanisms. In combination LEN may synergistically improve the efficacy of rituximab. However, there is limited data on the efficacy and safety of LEN in multi-drug combination regimens for treatment-naïve patients. We designed a phase II single arm trial to evaluate tumor response, toxicity (AE) and survival with a combination of LEN, rituximab, cyclophosphamide (CTX) and dexamethasone (DEX) (LR-CD) in symptomatic untreated patients with indolent B-cell lymphoma. (NCT00784927). Methods: Eligibility required age ≥18, ECOG PS ≤2, confirmed diagnosis of indolent B-cell lymphoma (FL1–2, SLL, MZL or LPL/WM), measurable nodes ≥2cm or IgM ≥400mg/dL (LPL/WM), ANC ≥1400/mm3, platelets ≥100,000/mm3, creatinine ≤2mg/dL, and signed informed consent. Only patients needing therapy were considered eligible. Treatment consisted of IV rituximab 375mg/m2 D1, oral LEN 20mg D1–21, CTX 250mg/m2 D1, 8, 15, DEX 40mg D1, 8, 15, 22 and ASA 325 mg daily in a 28 day cycle. Treatment continued 2 cycles beyond best response up to a maximum of 12 cycles. Toxicity was assessed by NCI CTCAE v3.0. Results: Thirty-one patients have enrolled at Mayo Clinic with 28 evaluable for toxicity and response (1 deemed ineligible, 1 withdrew before treatment, 1 treatment violation). Four patients continue on study at this time. Patient characteristics: median age 68.5(43–83), 71% male, stage IV 86%, FL 28%, MZL 25%, LPL/WM 39%, and SLL 4%. Median number of cycles given was 6 and 71% completed the study per protocol. The best overall response is 89% with 32% CR and 57% PR. In subgroup analysis, the response rates for LPL/WM was 91% (all PR) and for FL 88% (CR 63%, PR 25%). The most common grade ≥3 AEs were neutropenia (35.7%), leukopenia (17.8%), anemia (14.3%) and thrombosis (14.3%). The LPL/WM subgroup experienced more grade ≥3 anemia (36%) compared to the group as a whole. Patients (57%) required at least one dose reduction of LEN (n =10), CTX (n = 9) or DEX (n = 7). At a median f/u of 14.5 (1.8–36.5) months 86% are progression free (fig. 1) and the OS is 96% (fig. 2). One death unrelated to treatment occurred 7.7 months after completing 12 cycles of treatment. Conclusion: Lenalidomide can be safely combined with other active agents and in the combination LR-CD produces high response rates in symptomatic patients with indolent B-cell lymphoma. The regimen is well tolerated with manageable toxicities which are similar to that seen with single agent LEN. The encouraging results seen in patients with LPL/WM have led to expansion of this cohort for additional study. Disclosures: Reeder: Celgene: Research Funding. Off Label Use: lenalidomide use in non-Hodgkin lymphoma. Stewart:Celgene: Consultancy, Honoraria.

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 Our group recently reported a Phase III clinical trial (Porrata et al. Biology of Blood and Marrow Transplantation 2016; 22: 1017-1023) demonstrating that the infusion of the autograft-absolute lymphocyte count (A-ALC) and autograft natural killer cells (A-NKC) are survival prognostic factors in non-Hodgkin lymphoma (NHL) patients treated with autologous peripheral blood hematopoietic stem cell transplantation (APBHSCT). A limitation of our Phase III clinical trial was the short-term follow-up of just two years. Therefore, we evaluated longer follow-up and assessed the role of the infused A-ALC, infused A-NKC, and peripheral blood absolute natural killer cell count (ANKC) recovery on survival post-APBHSCT. Of the 122 patients that participated in the Phase III trial, 111 patients were able to complete APBHSCT and included in the current study. With a median follow-up of 57.2 months (range: 2.1-84.6 months), superior overall survival (OS) and progression-free survival (PFS) was observed in patients infused with an A-ALC ≥ 0.5 x 109 lymphocytes/kg [OS: HR = 0.429, 95%CI, 0.128-0.828, p < 0.01; and PFS: HR = 0.456, 95% CI, 0.177-0.863, p < 0.01] and an A-NKC ≥ 0.09 x 109 cells/kg [OS: HR = 1.58e-3, 95% CI, 1.046e-6-0.179, p < 0.003; and PFS: HR= 1.58e-3, 95% CI, 7.81e-7-0.064, p < 0.003]. Furthermore, patients that maintained an ANKC ≥ 250 cells/µl at 3 months, 6 months, 9 months and 12 months post-APBHSCT also experienced superior OS (Figure 1A) and PFS (Figure 1B)[OS and PFS times in months were evaluated from infusion date of stem cells]. In the multivariate analysis a sustained ANKC ≥ 250 cells/µl was an independent predictor for OS (HR = 0.013, 95% CI, 0.001-0.063, p < 0.0001) and PFS (HR = 0.014, 95% CI, 0.001-0.067, p < 0.0001). This study is an extension of our Phase III clinical trial showing that sustained innate immunity by measuring the ANKC correlated with superior clinical outcomes; thus providing a platform to develop innate immunity immunotherapeutic strategists directing to improve clinical outcomes post-APBHSCT in NHL patients. Figure 1 Figure 1. Disclosures No relevant conflicts of interest to declare.

Abstract Abstract 149 Background. There are few established factors that predict risk of follicular lymphoma (FL) transformation, and only two studies have evaluated the role of germline genetic variation and risk of transformation. One study reported an association of a BCL6 SNP (397C>G) with risk of transformation, and a second study reported an association with rs6457327, which is in the HLA region of 6p21. This study evaluated the risk of FL transformation in the modern treatment era with germline SNPs that were previously reported to be associated with FL transformation (BCL6SNPs and rs6457327), along with SNPs (N=45) previously associated with either risk of FL or FL prognosis. Methods. Newly diagnosed FL patients were prospectively enrolled from 2002–2009 into the Molecular Epidemiology Resource of the University of Iowa/Mayo Clinic Lymphoma SPORE. Peripheral blood for genotyping was collected at enrollment, and clinical and treatment data were abstracted from medical records. All patients were actively followed for disease progression, retreatment, transformation and death. For this analysis, only FL patients with grade I-IIIa were included. Patients with composite DLBCL, FL grade IIIb, or other evidence of transformation at diagnosis were excluded. Transformation was based on either 1) biopsy confirmation of FL grade IIIb, DLBCL, or higher grade B-cell lymphoma; or 2) clinical indicators of transformation based on the published literature, including sudden rise in LDH, rapid discordant localized nodal growth, new involvement of unusual extranodal sites, new B-symptoms, or hypercalcemia. Genotyping was conducted using a custom Illumina iSelect panel. Cox regression was used to estimate Hazard Ratios (HRs) and 95% confidence intervals (CI) for individual SNPs with time to transformation, with death modeled as a competing risk. Each SNP was modeled with the most prevalent homozygous genotype used as the reference group, and each SNP was modeled as having a log-additive (per minor allele) effect in the regression model. An ordinal test was used to assess the trend, and p<0.05 was considered statistically significant. Results. There were 631 newly diagnosed grade I-IIIa FL patients, of whom 532 had DNA and were successfully genotyped. The median age at diagnosis was 60 years (range 23–93) and 53% were male. FLIPI distribution was 42% 0–1, 34% 2 and 24% 3–5. Initial therapies included observation (32%), rituximab (R) monotherapy (13%), alkylator-based chemotherapy +/− R (20%), and anthracycline-based chemotherapy +/− R (19%). At a median of 59 months of follow-up (range, 11–110), 58 patients died, 254 had an event (death, progression or retreatment) and 54 patients (10%) transformed. Transformation was biopsy proven in 43 of the 54 patients (80%). The SNP rs6457327 on chromosome 6p that was previously reported to be associated with transformation was positively associated with risk of transformation in our data (HR=1.40; 95%CI 0.97–2.04; p=0.07), although this association was weaker but still consistent with the prior report. Further, we evaluated additional typed SNPs from the HLA region of 6p, and found additional associations (p<0.05) with HLA-DRA (3 SNPs), HLA-DQA2 (2 SNPs), HLA-DOA (2 SNPs) and HLA-DPB1/HLA-DPA2 (2 SNPs), of which rs10484569 from HLA-DPB1/HLA-DPA2 was the most strongly associated with risk of transformation (HR=3.01; 95%CI 1.48–6.09; p=0.002). None of the BCL6 or other previously reported risk SNPs were associated with transformation. Of the SNPs previously associated with FL prognosis, only the FCGR2A rs1801274 (HR=1.41; 95%CI 0.94–2.10; p=0.09) and CD46 (CD46 molecule, complement regulatory protein) rs2466571 (HR=1.72; 95%CI 1.16–2.55; p=0.007) were associated with risk of transformation. For CD46, one additional SNP (rs2796269) was also associated with transformation (HR=0.61; 95%CI 0.40–0.95; p=0.03). Further adjustment for FLIPI score and treatment (observation versus all other) did not alter these associations. Conclusions. The previously reported association of rs6457327 with risk of transformation in the modern treatment era was replicated. In addition, several HLA loci and two FL prognosis SNPs were linked to transformation risk. The remaining published FL risk or prognosis SNPs were not associated with transformation. Our results support a role for germline genetic variation in the HLA region, FCRGR2A and CD46 in transformation of FL. Disclosures: No relevant conflicts of interest to declare.

Abstract Abstract 1525 Background: Nodular lymphocyte predominant Hodgkin Lymphoma (NLPHL) is a more indolent form of Hodgkin Lymphoma that is usually associated with favorable outcomes. However, a number of reports have shown a tendency of transformation to more aggressive types of lymphoma, typically diffuse large B-cell lymphoma (DLBCL). Long-term data on the incidence and outcomes of transformed NLPHL is lacking in the literature. The aim of this study was to evaluate incidence, risk factors and outcomes of DLBCL transformation in NLPHL in a cohort of patients followed at a single institution. Methods: The actively maintained Mayo Clinic Lymphoma Database includes all consenting consecutive patients with lymphoma seen at Mayo Clinic Rochester. This was used to retrospectively identify patients with NLPHL. The study was approved by the Institutional Review Board. Pathology was reviewed by a hematopathologist and all transformations were histologically confirmed by WHO criteria. The clinical characteristics, therapy and outcomes of patients with NLPHL and DLBCL transformation were analyzed. The chi-square test was used to compare variables. Risk of progression was calculated using a person-year approach. Survival and freedom from transformation were estimated and compared using the Kaplan Meier method and log rank tests, respectively. Results: Between 1970 and 2010, 222 consecutive adult patients with NLPHL were identified. The median follow-up was 20 years. Of these, 17 (7.7%) developed a transformation to DLBCL during the course of the disease (Figure 1). The median time to transformation was 35 (6–248) months. Of these 17 patients, 13 (76.5%) were male, 11 (64.7%) had stage I/II and 6 (35.3%) had stage III/IV NLPHL. Transformation was the first relapse in most patients (12 patients, 70.6%) while five patients (29.4%) developed one or more relapses of NLPHL before transformation. Prior therapies for NLPHL were as follows: radiation therapy in 5 (29.4%), chemotherapy in 5 (29.4%) and combined chemotherapy and radiation in 6 (35.3%) patients. The median age at transformation was 45 years (30–87). Most patients (10 patients, 58.8%) presented with signs (palpable lymph nodes) or “B” symptoms. Eight patients (47.1%) had stage III/IV disease at the time of transformation. The most commonly used regimens for treatment of DLBCL were R-CHOP or CHOP (9 patients, 52.9%). Platinum based therapy was administered in 4 (23.5%) patients. Five patients (29.4%) required more than one line of therapy, and autologous stem cell transplant was utilized in two (11.7%) patients. Based on the observed 17 transformations during 2304 patient-years of follow-up, the rate of transformation was 0.74 per 100 patient-years. The five-year overall survival (OS) of patients with transformed disease (calculated from time of transformation) was 76.4%. The most common cause of death was lymphoma (75%). Following treatment for transformation, 5 patients (29.4%) relapsed. The OS in transformed patients was independent of prior therapies, and transformation did not adversely affect overall survival in our cohort (median survival of in 129 months in transformed versus 120 in non-transformed patients, P=0.33). In a univariate analysis of prior therapies, use of radiation therapy was associated with a significant delay in time to transformation (P= 0.0035) (Table 1, figure 2). Conclusions: The risk of transformation in NLPHL is 0.74% per year in this large single institution case series of NLPHL, and appears to be lower than that observed in follicular and other types of low grade lymphoma. The outcomes of patients with transformation were significantly better than reported in other types of transformed lymphoma and did not adversely affect OS. Disclosures: No relevant conflicts of interest to declare.

Abstract Abstract 1563 Intro: Optimal treatment for non-follicular low grade B-cell lymphoma (NFLGL) is not well defined. Clinical trial design for these subtypes would be enhanced by further understanding of early presentation and management. A large prospective observational study was used to identify presenting clinical features, describe patterns of care and compare the prognostic utility of International Prognostic Index (IPI) and the Follicular Lymphoma International Prognostic Index (FLIPI). Methods: The University of Iowa/Mayo Clinic SPORE Molecular Epidemiology Resource (MER) is a prospective, longitudinal observational study designed to collect information on patterns of care and outcomes for patients with newly diagnosed lymphoma. Patients seen at the Mayo Clinic, Rochester MN and the University of Iowa within 9 months of their initial diagnosis of lymphoma are offered enrollment. Baseline patient reported data, clinical data and initial management are collected using a standard protocol and a central pathology review is performed. After enrollment, patients are actively followed for events (disease progression, retreatment, and death) and disease related comorbidities. This analysis includes 198 patients diagnosed with extranodal marginal zone (EMZL), 22 with nodal marginal zone (NMZL), 47 with splenic marginal zone (SMZL), 48 with lymphoplasmacytic lymphoma (LPL), as well as 67 patients with unclassifiable low-grade B-cell lymphoma (B-NOS). Results: 382 newly diagnosed NFLGBL patients were enrolled in the MER from 2002–2009. The median age at enrollment was 63 years (range 22–95). 52% were male. The most common types of initial therapy after diagnosis were observation (41 %), alkylator- based chemotherapy +/− rituximab (R) (17%), radiation therapy alone (15%) and R monotherapy (13%). At median follow-up of 60 months (range 1–121), 51 patients were deceased and 155 had an event. The clinical characteristics that comprise the IPI and FLIPI were similar across the subtypes. Approximately half of the cases presented at low risk (55% IPI; 48% FLIPI). A majority had a normal LDH (81%), limited nodal involvement (91% had ≤ 4 groups), normal hemoglobin (71% ≥12 g/dL), good performance status (95% 0–1), and advanced stage (57% stages III-IV). There were notable differences among the NFLGBL subtypes. Patients with SMZL and LPL presented with high risk FLIPI of 3–5 (49% and 46% respectively) and high to high-intermediate IPI of 3–5 (21% and 13%). Abnormal LDH and anemia (< 12 g/dL) were more frequent in patients with SMZL (40%; 56%) and LPL (25%; 62%). EMZL presented with lower stages (70% stage I-II) and NMZL presented with increased nodal involvement (38% >4 sites). SMZL had the highest rates of surgical resection (21%) and EMZL was more frequently treated with radiation therapy (25%). LPL (30%) and NMZL (32%) more commonly received alkylator based chemotherapy +/− R. While both IPI and FLIPI differentiated outcome in these patients, FLIPI had higher c-statistics than IPI for both EFS (0.583 vs 0.568) and OS (0.685 vs 0.661), respectively. Conclusions: This large prospective collection of data on NFLGBL patients presenting to academic medical centers provides a modern picture of presentation and management patterns useful to investigators designing clinical trials. FLIPI may have more prognostic utility than IPI in this group of patients. Disclosures: Ansell: Seattle Genetics, Inc.: Research Funding.

Abstract Results from the Phase I portion of this study in high risk chronic lymphocytic leukemia (CLL) patients (pts) (NCT01269385) showed that the combination of Imprime PGG (IPGG) at doses up to 4 mg/kg, with alemtuzumab (ALM) and rituximab (RTX), was well tolerated and associated with a 73% complete response (CR) rate (Blood 120: Abstr 1792, 2013). IPGG is a yeast-derived beta 1,3/1,6 glucan that engages innate immune cells, enhancing anti-tumor activity in combination with complement activating monoclonal antibodies (mAb) via a mechanism involving complement receptor 3 (J Immunol 177:1661, 2006). Endogenous anti-beta glucan antibodies (ABA) are required for IPGG binding to complement receptors and modulation of innate immune cell function. In pts with stage IV non-small cell lung cancer (NSCLC), correlation between serum ABA concentrations and response to an IPGG-containing frontline regimen has been observed (J Clin Oncol 32: 15S; Abstr 3045, 2014). Here we report clinical and translational results at the end of the Phase II portion of this CLL study. Methods: The primary endpoint of the Phase II study was the proportion of pts experiencing CR 3 months after completing 5 weeks of treatment with IPGG 4 mg/kg, ALM and RTX. Eligible pts (n=14) had a diagnosis of CLL by standard criteria (IWCLL-NCI 2008), no prior treatment for CLL, high risk CLL based on molecular markers (17p13-; 11q22-; unmutated [<2%] IGHV and/or use of VH3-21 AND CD38+ [³30%] and/or ZAP70+ [³20%]), no standard indication for initiation of CLL therapy, and adequate performance status and organ function. Planned enrollment was up to 39 pts but the study was terminated early due to slow accrual. Translational studies evaluated baseline serum ABA levels and in vitro binding of IPGG to immune cell subsets in whole blood. Results: The median age was 63.5 (range 47-77); 71% were male; and 6 (43%), 5 (36%) and 3 (21%) pts had Rai Stage 0, 1 and 2, respectively. CLL high-risk parameters were 17p13- in 3 (21%), 11q22- in 5 (36%), and unmutated IGHV or use of VH3-21 together with either expression of ZAP70 and/or CD38 in 6 (43%) pts. Grade 3 AEs were diarrhea (n=3) and increased transaminase levels, dehydration, gastritis, hypertension, hyponatremia, and hypertension (each n=1). Grade 4 AEs were neutropenia (n=2) and febrile neutropenia (n=1). Thirteen (93%) patients responded to therapy, with 7 CR, 2 CR with incomplete marrow recovery, 1 nodular PR and 3 PR (IWCLL-NCI 2008 criteria). Median follow-up was 12.7 mo (range 6.7 - 28.0). The overall median duration of response cannot be determined, as only 5/13 responders have progressed (median of 5.6 mo; range: 2.9 - 8.5) and the other 8 remain progression-free after a median of 8.0 mo (range 5.6 - 21.0). Four progressing pts were retreated after a median of 14.2 mo (range 12.4 - 20.5). There were no deaths during or after treatment. Translational studies demonstrated a correlation between ABA concentrations and binding of IPGG to neutrophils, monocytes and B-cells. However, there was no correlation between ABA concentrations and response to treatment. Potential functional implications of binding of IPGG to leukemic B cells, including direct and indirect enhancement of the antibody-dependent cellular cytotoxicity and antibody-dependent cellular phagocytosis mediated by anti-tumor mAbs are under investigation. Discussion: The combination of IPGG with ALM and RTX appeared safe and well tolerated overall with an ORR of 93% and a 64% CR/CRi rate. ABA concentrations did not correlate with clinical response to an IPGG containing regimen in these CLL patients. Data on functional implications of IPGG binding to leukemic B cells will be presented. Disclosures Bose: Biothera: Corporate stock options Other, Employment, Research Funding. Zent:Biothera: Research Funding. Ottoson:Biothera: Corporate stock options Other, Employment. Leonardo:Biothera: Corporate stock options Other, Employment. Ansell:Biothera: Research Funding.

Abstract BACKGROUND: Diffuse large B-cell lymphoma, not otherwise specified (DLBCL), though defined as one disease entity, consists of two main cell-of-origin (COO) subtypes, germinal center B-cell like (GCB) and activated B-cell like (ABC), with the latter predicting a significantly worse prognosis using conventional chemotherapy. Up to 40% of all patients diagnosed with DLBCL will experience relapse, and outcomes are generally poor in this setting. In this study, we examine the proportion of GCB vs. non-GCB subtypes at initial diagnosis and at time of relapse, and assess the incidence of reclassification from one subtype to another. METHODS: Patients were prospectively enrolled in the University of Iowa/Mayo Clinic SPORE Molecular Epidemiology Resource (MER) within 9 months of diagnosis and followed for relapse, retreatment, and death. All relapse events were validated by review of the medical record. This analysis includes patients diagnosed with DLBCL who underwent initial treatment and subsequently experienced relapse as confirmed by biopsy. Immunohistochemical staining data including CD10, Bcl-6, and Mum-1, were collected from available pathology reports and classified to either GCB or non-GCB subtypes as predicted by the Hans algorithm. We compared subtype classification and individual immunohistochemical data both at the time of diagnosis and relapse. The overall subtype agreement between the two diagnostic time points was assessed. RESULTS: 1023 patients with newly diagnosed DLBCL were enrolled in the MER from 2002 - 2012. Of those, 249 had documented disease relapse. Of those analyzed, a total of 43 patients had COO classification based on the Hans algorithm from tissue biopsy at both diagnosis and relapse. Thirty patients were characterized as GCB DLBCL on initial presentation, and upon relapse 28 were noted to be GCB, while 2 were noted to be the non-GCB subtype. Of the 13 that were characterized as non-GCB on initial presentation, 10 remained non-GCB while 3 were reclassified as GCB. The overall agreement of DLBCL COO phenotypes between initial diagnosis and relapse was 88%. Seven percent of those initially diagnosed as GCB were reclassified as non-GCB subtype; in contrast, 23% of those initially diagnosed as non-GCB had changed to GCB upon relapse. Similar analysis was performed on individual immunohistochemical staining factors including CD10, Bcl-6, and Mum-1, and we observed overall agreement of 88%, 87%, and 91%, respectively. CONCLUSIONS: A majority of patients with relapsed DLBCL exhibit similar COO phenotypes at initial presentation and at relapse, and the incidence of reclassification from one subtype to another is uncommon. This suggests that the initial treatment regimen for DLBCL rarely alters the basic cancer phenotype when immunohistochemistry laboratory technical factors and pathologist interpretive discrepancies are excluded as causes for this change. However, reclassification from GCB to non-GCB subtypes is observed in a minority of cases, which may affect the overall outcome and response to treatment. Further studies are needed using gene expression to categorize COO and to examine the factors surrounding the time of relapse for possible harbingers of relapse as well as the behavior and outcome of reclassified DLBCL. Table Table. Disclosures Ansell: BMS, Seattle Genetics, Merck, Celldex and Affimed: Research Funding.