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Objective The aim of this study was to grade cartilage damage in a swine model of osteoarthritis using a whole-body photon-counting detector (PCD) CT. Materials and Methods A multienergy phantom containing gadolinium (Gd) (2, 4, 8, and 16 mg/mL) and hydroxyapatite (200 and 400 mg/cc) was scanned using a PCD-CT system (48 × 0.25 mm collimation, 80 kV, 800 mAs, D50 reconstruction kernel) to serve as calibration for material decomposition and to assess quantification accuracy. Osteoarthritis was induced in Yucatan miniswine (n = 8) using 1.2 mg monoiodoacetate (MIA) injected into a randomized knee, whereas the contralateral control knee received saline. Twenty-one days later, a contrast bolus (gadoterate meglumine, 4 mL/knee) was intra-articularly administered into both knees. The knees were simultaneously scanned on the PCD-CT system (48 × 0.25 mm collimation, 80 kV, 800 mAs). Multienergy images were reconstructed with a sharp “V71” kernel and a quantitative “D50” kernel. Image denoising was applied to the V71 images before grading cartilage damage, and an iterative material decomposition technique was applied to D50 images to generate the Gd maps. Two radiologists blinded to the knee injection status graded the cartilage integrity based on a modified International Cartilage Repair Society scoring system. Histology was performed on excised cartilage using methylene blue/basic fuchsin. Statistical analysis of grade distribution was performed using an exact test of omnibus symmetry with P < 0.05 considered significant. Results Material decomposed images from the multienergy phantom scan showed delineation and quantification of Gd and hydroxyapatite with a root-mean-squared error of 0.3 mg/mL and 18.4 mg/cc, respectively. In the animal cohort, the radiologists reported chondromalacia in the MIA knees with International Cartilage Repair Society scores ranging from grade 1 (cartilage heterogeneity, n = 4 knees) to grade 3 (up to 100% cartilage loss, n = 4 knees). Grade 1 was characterized by cartilage heterogeneity and increased joint space in the patellofemoral compartment, whereas grade 3 was characterized by cartilage erosion and bone-on-bone articulation in the patellofemoral compartment. All control knees were scored as grade 0 (normal cartilage). Significant difference (P = 0.004) was observed in the grade distribution between the MIA and control knees. Gross examination of the excised knees showed cartilage lesions in the grade 3 MIA knees. The Gd maps from material decomposition showed lower contrast levels in the joint space of the MIA knee compared with the contralateral control knee due to joint effusion. Histology revealed chondrocyte loss in the MIA knee cartilage confirming the chondrotoxic effects of MIA on cartilage matrix. Conclusions We demonstrated a high-resolution and quantitative PCD-CT arthrography technique for grading cartilage damage in a large animal model of osteoarthritis. Photon-counting detector CT offers simultaneous high-resolution and multienergy imaging capabilities that allowed morphological assessment of cartilage loss and quantification of contrast levels in the joint as a marker of joint disease. Cartilage damage in the MIA knees was graded using PCD-CT images, and the image-based findings were further confirmed using histology and gross examination of the excised knees.

Objective The aim of this study was to quantitatively demonstrate radiation dose reduction for sinus and temporal bone examinations using high-resolution photon-counting detector (PCD) computed tomography (CT) with an additional tin (Sn) filter. Materials and Methods A multienergy CT phantom, an anthropomorphic head phantom, and a cadaver head were scanned on a research PCD-CT scanner using ultra-high-resolution mode at 100-kV tube potential with an additional tin filter (Sn-100 kV) and volume CT dose index of 10 mGy. They were also scanned on a commercial CT scanner with an energy-integrating detector (EID) following standard clinical protocols. Thirty patients referred to clinically indicated sinus examinations, and two patients referred to temporal bone examinations were scanned on the PCD-CT system after their clinical scans on an EID-CT. For the sinus cohort, PCD-CT scans were performed using Sn-100 kV at 4 dose levels at 10 mGy (n = 9), 8 mGy (n = 7), 7 mGy (n = 7), and 6 mGy (n = 7), and the clinical EID-CT was performed at 120 kV and 13.7 mGy (mean CT volume dose index). For the temporal bone scans, PCD-CT was performed using Sn-100 kV (10.1 mGy), and EID-CT was performed at 120 kV and routine clinical dose (52.6 and 66 mGy). For both PCD-CT and EID-CT, sinus images were reconstructed using H70 kernel at 0.75-mm slice thickness, and temporal bone images were reconstructed using a U70 kernel at 0.6-mm slice thickness. In addition, iterative reconstruction with a dedicated sharp kernel (V80) was used to obtain high-resolution PCD-CT images from a sinus patient scan to demonstrate improved anatomic delineation. Improvements in spatial resolution from the dedicated sharp kernel was quantified using modulation transfer function measured with a wire phantom. A neuroradiologist assessed the H70 sinus images for visualization of critical anatomical structures in low-dose PCD-CT images and routine-dose EID-CT images using a 5-point Likert scale (structural detection obscured and poor diagnostic confidence, score = 1; improved anatomic delineation and diagnostic confidence, score = 5). Image contrast and noise were measured in representative regions of interest and compared between PCD-CT and EID-CT, and the noise difference between the 2 acquisitions was used to estimate the dose reduction in the sinus and temporal bone patient cohorts. Results The multienergy phantom experiment showed a noise reduction of 26% in the Sn-100 kV PCD-CT image, corresponding to a total dose reduction of 56% compared with EID-CT (clinical dose) without compromising image contrast. The PCD-CT images from the head phantom and the cadaver scans demonstrated a dose reduction of 67% and 83%, for sinus and temporal bone examinations, respectively, compared with EID-CT. In the sinus cohort, PCD-CT demonstrated a mean dose reduction of 67%. The 10- and 8-mGy sinus patient images from PCD-CT were significantly superior to clinical EID-CT for visualization of critical sinus structures (median score = 5 ± 0.82 and P = 0.01 for lesser palatine foramina, median score = 4 ± 0.68 and P = 0.039 for nasomaxillary sutures, and median score = 4 ± 0.96 and P = 0.01 for anterior ethmoid artery canal). The 6- and 7-mGy sinus patient images did not show any significant difference between PCD-CT and EID-CT. In addition, V80 (sharp kernel, 10% modulation transfer function = 18.6 cm −1 ) PCD-CT images from a sinus patient scan increased the conspicuity of nasomaxillary sutures compared with the clinical EID-CT images. The temporal bone patient images demonstrated a dose reduction of up to 85% compared with clinical EID-CT images, whereas visualization of inner ear structures such as the incudomalleolar joint were similar between EID-CT and PCD-CT. Conclusions Phantom and cadaver studies demonstrated dose reduction using Sn-100 kV PCD-CT compared with current clinical EID-CT while maintaining the desired image contrast. Dose reduction was further validated in sinus and temporal bone patient studies. The ultra-high resolution capability from PCD-CT allowed improved anatomical delineation for sinus imaging compared with current clinical standard.

Introduction. Acquired severe aplastic anemia (SAA) is a life-threatening disorder characterized by severe progressive pancytopenia and hypocellular bone marrow. The etiology of acquired SAA is not understood but believed to be related to abnormal immune responses to environmental exposures. We conducted a genome-wide association study (GWAS) to identify common germline variants associated with SAA. Methods. We identified 895 patients with SAA who underwent related or unrelated hematopoietic cell transplant (HCT) with clinical data and pre-HCT blood samples available in the Center for International Blood and Marrow Transplant Research (CIBMTR) database and biorepository. Pre-HCT DNA was extracted from blood of patients with SAA and genome-wide genotyping was conducted using the Illumina OmniExpress array. We excluded 93 inherited bone marrow failure cases. The SAA cases were grouped cases into discovery and validation sets based on time of batch sample receipt. Analyses were limited to patients of European ancestry based on principal component analyses to minimize the potential effect of population stratification. Controls were genomically matched and selected from previously scanned cancer-free subjects at the Cancer Genomics Research Laboratory, Division of Cancer Epidemiology and Genetics, NCI. The final analysis included 534 acquired SAA cases (359 in the discovery set and 175 in the validation set), and 2,455 controls (1,396 in the discovery set, and 1,059 in the validation set). Results. Patients with SAA in this study received HCT between 1989-2015 at a median age of 21 years, 56% were male, and the median time between SAA diagnosis and HCT was 11 months. Strong genome-wide association signals were identified across the human leukocyte antigen (HLA) genes encoded at the major histocompatibility complex (MHC) on chromosome 6p21 (Figure 1). The top SNP was located in the P4 binding pocket of the HLA class II gene HLA-DPB1(rs1042151A>G, p.Met105Val, pooled-odds ratio [OR]=1.75, 95% confidence interval [CI]=1.50-2.03, p=1.94x10-13). The expression of HLA-DP in CD19+ cells from 175 healthy donors was significantly different by rs1042151 A>G genotype (p=2.04x10-6) (Figure 2). A second SNP near HLA-B, rs28367832G>A, also reached genome-wide significance (pooled-OR=1.49, 95% CI=1.22-1.78, p=7.27x10-9). Copy-number variant analysis and next generation sequencing also identified somatic, clonal copy-neutral loss-of-heterozygosity affecting class I HLA genes in 8.6% of the SAA cases and none of the controls. Conclusion. This SAA GWAS identified strong association signals between common germline genetic variants in HLA class I and II genes and SAA. The main SNP is associated with changes in HLA-DP expression suggesting a key role for this locus in SAA etiology. This study adds further evidence to the connection between SAA and immune dysregulation. Disclosures Cerhan: Janssen: Membership on an entity's Board of Directors or advisory committees; NanoString: Research Funding; Celgene: Research Funding. Lee:Incyte: Research Funding; Syndax: Research Funding; Amgen: Research Funding; Novartis: Research Funding; Takeda: Research Funding; Kadmon: Consultancy, Research Funding; Pfizer: Consultancy, Research Funding; AstraZeneca: Research Funding.

Introduction Renal dysfunction is a recognized risk factor for mortality after HCT, as it is included in the comorbidity index (HCT CI). Yet, further understanding on outcomes in patients with different level of renal dysfunction or undergoing hemodialysis (HD) at time of transplant remains scant. This study explores the impact of different levels renal dysfunction on major HCT outcomes in a large population using data reported to the Center for International Blood and Marrow Transplant Research (CIBMTR). Methods The study population included 8,102 patients age 40 years and older who received HCT for treatment of malignancies from 2008 to 2016, with available pre-transplant creatinine measurement. eGFR, calculated using CKD-EPI (CKD-epidemiology collaboration) method, was used to assigned patients in four categories: eGFR ≥ 90ml/min (eGFR≥ 90, N=4,237, reference), eGFR 60-90ml/min (eGFR 60-90, N=3,158), eGFR 45-59ml/min (eGFR 45-59, N=538) and eGFR <45ml/min(eGFR<45, N=169). A separate cohort of patients on HD at time of HCT (N=46) was analyzed independently. Multivariate analysis models were built for assessment of overall mortality, transplant-related mortality (TRM), disease relapse or progression, graft-versus-host disease (GVHD), hepatic sinusoidal obstructive syndrome (SOS), thrombotic microangiopathy (TMA), idiopathic pneumonia syndrome (IPS) and need of HD post-transplant. Common patient-, disease- and transplant-related covariates were tested on all models and HCT CI was computed without reported renal dysfunction comorbidity to avoid collinearity. Results Patient characteristics are shown in table 1. The groups were comparable on disease risk index, graft and donor source, but patients with eGFR>90 were younger and received myeloablative conditioning more frequently. The cohort of eGFR <45 had a higher proportion of patients with HCT CI ≥3. TRM and overall survival according to eGFR groups are shown in Figure. In the multivariate analysis models eGFR as the main effect was associated with TRM (p<0.0001), overall mortality (p<0.0001), and requirement of HD post HCT (p<0.0001), but not for relapse/progression (p=0.98), GVHD (grades II-IV, p=0.34; III-IV, p=0.70; and chronic, p=0.20), TMA (p=0.46), SOS (p=0.02) or IPS (p=0.06). Compared to eGFR ≥90, the hazard ratio (HR) for TRM for eGFR 60-89 was 1.12 (p=0.07), for eGFR 45-59 was 1.46 (p<0.001) and for eGFR<45 was 1.74 (p=0.004). Corresponding HRs for overall mortality were 1.0 (p=0.9), 1.17 (p=0.03) and 1.63 (p<0.0001), respectively. Similarly, for the need of HD post HCT, HR for eGFR60-89 was 1.29 (p=0.03), eGFR45-59 was 2.45 (p<0.001) and for eGFR<45 was 3.09 (p<0.0001). Only eGFR<45 was associated with higher risk of SOS (HR2.66, p=0.03). Among 46 patients on HD prior to HCT, one-year probability of overall survival was 20% (95% Confidence Interval [CI] 10-32%) and cumulative incidence of TRM at one year was 67% (95% CI, 50-81%). Conclusion These findings indicate that degree of renal dysfunction is an independent predictor of OS, TRM, probability of receiving HD and SOS when adjusted for other risk factors. The impact of eGFR on the need of HD, a complication that increases morbidity post HCT is an important finding. Additionally, the outcomes of a subset of patients on HD at time of transplants are dismal. These results can further assist the prognostic assessment of candidates for an allogeneic HCT. Disclosures Stadtmauer: Celgene: Consultancy; Takeda: Consultancy; Janssen: Consultancy; Amgen: Consultancy; Novartis: Consultancy, Research Funding; Tmunity: Research Funding; Abbvie: Research Funding. Wingard:Ansun: Consultancy; Pluristem: Consultancy; Celgene: Consultancy; Merck: Consultancy; Shire: Consultancy. Ganguly:Seattle Genetics: Speakers Bureau; Daiichi Sankyo: Research Funding; Kite Pharma: Honoraria, Other: Advisory Board; Janssen: Honoraria, Other: Advisory Board. Pasquini:Pfizer: Other: Advisory Board; Amgen: Consultancy; Medigene: Consultancy; BMS: Research Funding; Novartis: Research Funding; Kit Pharma: Research Funding.

Abstract Purpose: Prior neoadjuvant trials with 12 weeks of dual anti-HER2 therapy without chemotherapy demonstrated a meaningful pathologic complete response (pCR) in patients with HER2-positive breast cancer. In this trial, we sought to determine whether longer treatment would increase the rate of pCR. Patients and Methods: TBCRC023 (NCT00999804) is a randomized phase II trial combining a Simon phase II design in the experimental arm with a pick-the-winner design, not powered for direct comparison. Women with HER2-positive breast tumors measuring ≥2 cm (median = 5 cm) were randomized in a 1:2 ratio to 12 versus 24 weeks of lapatinib and trastuzumab. Letrozole (along with ovarian suppression if premenopausal) was administered in patients whose tumors were also estrogen receptor (ER) positive. All evaluable patients were assessed for in-breast pCR. Results: Ninety-seven patients were enrolled (33 in 12-week arm and 64 in 24-week arm), of whom 94 were evaluable. Median age was 51 years, and 55% were postmenopausal. Median tumor size was 5 cm, and 65% were ER-positive. The rate of pCR in the 24-week arm was 28% and numerically superior to the 12-week arm (12%). This was driven by increased pCR in the ER-positive subgroup (33% vs. 9%). Study treatment was well tolerated, with grade 1–2 diarrhea and acneiform rash being the most common toxicities. Conclusions: Treatment with dual anti-HER2 therapy for 24 weeks led to a numeric increase in pCR rate in women with HER2-positive breast cancer, without using chemotherapy. If validated, this approach may help identify patients who may benefit from deescalation of therapy.

Abstract Abstract 467 Background: While donor-recipient disparity at HLA loci is associated with greater risk for severe acute graft vs. host disease (GVHD) and inferior survival after unrelated donor allogeneic hematopoietic cell transplantation (HCT), the impact of amino acid substitution (AAS) at peptide binding pockets of the HLA molecule is incompletely understood. Methods: Adult and pediatric patients who received myeloablative or reduced intensity/non-myeloablative first unrelated bone marrow or peripheral blood stem cell transplantation for AML, ALL, CML or MDS between 1988 and 2009 were included. Donors and patients were fully high resolution matched for HLA-A, B, C, and DRB1 (8/8) or had single mismatch (7/8) at one HLA class I locus. Among 7/8 donor-recipient pairs, cases were categorized based on the presence or absence of the AAS of interest at positions 9, 77, 99, 116, or 156 of the class I molecule. In multivariable analysis accounting for patient, disease, and transplantation variables, we studied the independent impact of AAS at these residues on risk for grade III-IV acute GVHD, chronic GVHD, treatment-related mortality, primary malignancy relapse, and overall survival. We compared 7/8 donor-recipient pairs with AAS of interest to 7/8 pairs without these AAS in the primary analyses. Additionally, we performed this analysis restricted to each HLA class I locus. Results: Donor-recipient pairs were 8/8 matched (n=5282), 7/8 with AAS of interest (n=1713), or 7/8 without AAS of interest (n=318). In multivariable analysis, AAS at position 116 was associated with increased risk for grade III-IV acute GVHD (HR 1.21, 1.04–1.42, p=0.0165). No other significant association was detected between AAS studied and clinical outcomes. In multivariable analysis restricted to each class I HLA locus, we detected the following: Among 7/8 matched pairs with mismatch at HLA-C, AAS at position 116 was associated with increased risk for severe acute GVHD (HR 1.42, 1.13–1.79, p=0.0031) and inferior OS (HR 1.2, 1.01–1.41, p=0.0343). AAS at position 99 was associated with increased TRM (HR 1.37, 1.11–1.69, p=0.0037). Of 7/8 pairs with mismatch at HLA-B, AAS at position 9 was associated with increased chronic GVHD (HR 2.19, 1.31–3.66, p=0.0029). Specific amino acid substitution pairs with frequency > 30 were tested for association with HCT outcomes. None met the significance level of 0.00125, pre-specified for multiple comparisons. Conclusions: These results support the concept that AAS at key peptide-binding residues in the HLA class I molecule are associated with increased risk for severe acute GVHD and lower survival. Disclosures: No relevant conflicts of interest to declare.

Abstract Background: Conflicting data exists on whether T-cell dose of allogeneic stem cell product influences transplant outcome. Methods: Using CIBMTR database, we identified 2,736 adult patients who underwent first allogeneic HCT for AML/ALL/MDS (between 2008-2014) with PBSC from an HLA-identical sibling donor (MSD) or 8/8-matched unrelated donor (MUD). This cohort excluded ex-vivo and in-vivo T-cell depletion transplants. Correlative analysis was done between CD3 cell dose and risk of GVHD, relapse, NRM, DFS and OS. Results: T-cell dose cutoff values were identified (using maximum likelihood estimation method) to identify differential risk of aGVHD (grade II-IV) in both MSD and MUD groups. A CD3 cell dose cutoff of 14 x107 cells/kg identified MSD/low CD3 (n=223) and MSD/high CD3 (n=1214) and a dose of 15 x107 cells/kg identified MUD/low CD3 (n=197) and MUD/high CD3 (n=1102). CD3 and CD34 cell doses did not correlate. Median CD3 cell dose were 11 and 29 in the MSD/Low and MSD/High groups, respectively, and 10 and 28 in the MUD/Low and MUD/High groups, respectively. In MSD/high CD3, cumulative incidence (CI) of D100-aGVHD (GII-IV) was higher (33% vs 25%) (P value =0.009) without influence on engraftment, severe aGVHD (GIII-IV), cGVHD, NRM, relapse, DFS, or OS. In MUD/high CD3, CI of D100-aGVHD (GII-IV) was higher (50% vs 40%) (p value=0.009) and so was the CI of 6-month-cGVHD (31% vs23%) (p value = 0.02) with no influence on engraftment, severe aGVHD, 2-year-GVHD, NRM, relapse, DFS, or OS. On multivariate analysis, both MSD (table 1) and MUD (table 2) groups failed to show a correlation between CD3 cell dose and aGVHD (GII-IV) (p value =0.1 and 0.07), cGVHD (p value=0.8 and 0.3) for both groups respectviely. Sub-analysis of CD4, CD8 and CD4/CD8 ratio failed to identify cutoff values predictive of transplant outcome. Using log-rank test, the sample size was, however, suboptimal to identify difference (with 80% power at 0.05% significant level) at these cutoff cell dose. Conclusion: In this relatively small registry study, the CD3 cell dose in the PBSCT product did not influence the risk of acute or chronic GVHD or other transplant outcome when using matched sibling or 8/8 unrelated donors. Disclosures Saad: Actinium: Consultancy. Lamb:Incysus Therapeutics Inc.: Consultancy, Equity Ownership, Membership on an entity's Board of Directors or advisory committees, Research Funding.

Abstract Background: Obesity is increasing in prevalence worldwide and has potential implications on chemotherapy dosing and selection of patients for therapy. Auto HCT improves outcomes for patients with MM, but optimal chemotherapy dosing for obese patients is poorly defined. Methods: We identified 1087 patients reported to the CIBMTR between 1995 and 2003 who underwent auto HCT for MM as part of initial therapy, defined as within 18 months of diagnosis, and received high-dose melphalan conditioning, with or without total body irradiation (TBI). We categorized patients by body mass index (BMI) as normal (18.5– 24.9), overweight (25–29.9), obese (30–34.9), or severely obese (≥35). Underweight patients (BMI <18.5, N=9) were excluded from analysis. We analyzed overall survival (OS) and progression-free survival (PFS) from date of transplant, using Kaplan-Meier curves and the log-rank test for univariate analyses and using Cox proportional hazards models for multivariate analyses. Results: Cases were reported from 114 centers in 10 countries. There were 292 patients of normal weight (27%); 472 were overweight (43%), 198 were obese (18%), and 125 severely obese (11%). Median follow-up of survivors was 63, 61, 60 and 59 months, respectively. Significant baseline differences among BMI groups indicate that obese patients selected for transplant were younger (median age 58, 58, 56, and 55 years, respectively, p=0.005) and had less severe disease at diagnosis, with lower bone marrow plasmacytosis and less frequent renal failure, hypercalcemia, and severe anemia. Obese patients received higher total melphalan doses but lower doses per square meter of body surface area (calculated based on actual body weight). Univariate analyses show no significant effect of BMI category on either OS or PFS. However, among patients who received TBI as part of conditioning, multivariable analyses show a significant effect of BMI on PFS (p-value for interaction 0.006). In this subgroup, a higher BMI was associated with longer PFS (p=0.006, Figure 1). Among patients who received melphalan alone, no effect of BMI was apparent (Figure 2). The difference in PFS for patients receiving melphalan/TBI was due to a decreased risk of relapse among obese patients. Pairwise comparisons of conditioning regimen (TBI vs. no TBI) within BMI categories showed significant reduction in risk of treatment failure for obese (HR=0.54, p=0.04) and severely obese (HR=0.32, p=0.001) patients who received TBI. No differences in OS were apparent in multivariate analyses. Relative risks (RR) for PFS from a multivariable model adjusting for possible confounders are shown below: TBI No TBI n RR (95% CI) P n RR (95% CI) P Normal 44 1.00 Poverall=0.006 248 1.00 Poverall=0.18 Overweight 62 0.92 (0.60–1.40) 0.69 405 0.90 (0.75–1.08) 0.24 Obese 21 0.49 (0.27–0.90) 0.021 177 0.85 (0.68–1.07) 0.16 Severely obese 22 0.39 (0.20–0.76) 0.005 100 1.12 (0.86–1.45) 0.42 Conclusion: Obesity, when measured by BMI, has no statistically significant effect on OS among patients with myeloma receiving high-dose melphalan. Among patients receiving melphalan with TBI, a higher BMI is associated with improved PFS. The reason for the restriction of this effect to TBI-containing conditioning regimens requires further investigation. The current common strategy of reducing melphalan doses (i.e. calculating based on ideal or adjusted body weight) does not appear to impair outcomes for obese patients. Obesity should not exclude patients from consideration of autologous transplantation. Figure Figure

Abstract Background: Peripheral T-cell lymphoma (PTCL) is a heterogeneous group of non-Hodgkin lymphomas associated with poor prognosis and repeated recurrence for most subtypes. Currently, anthracycline-based therapies such as cyclophosphamide, doxorubicin, vincristine and prednisone (CHOP) or CHOP-like therapies are recommended as the first-line treatment for PTCL, but the prognosis remains poor with most patients relapsing within 5 years. Thus, improved treatment strategies are still needed. Belinostat is a potent, pan-histone deacetylase inhibitor that was recently approved in the United States for the treatment of patients with relapsed or refractory PTCL (R/R PTCL). Approval was based on results from the pivotal Phase 2 BELIEF study (O'Connor et al, JCO, 2015) of belinostat in R/R PTCL, which demonstrated durable clinical benefit (objective response rate [ORR] 25.8%) and tolerability. Since belinostat (Bel) and each of the components of the CHOP regimen target different aspects of the cell cycle with different mechanisms of action, there is potential for a synergistic effect of a Bel-CHOP combination treatment regimen for patients with PTCL. Methods: Patients with PTCL received CHOP in association with 1000 mg/m2 of belinostat on various schedules, repeated every 21-days for up to 6 cycles. The cohort schema followed a traditional "3+3" dose escalation design. The objective of Part A of the study was to determine the Maximum Tolerated Dose (MTD) of the Bel-CHOP combination. Once the MTD was determined, at least 10 more patients were to be treated in the Expansion Phase (Part B). Belinostat was to be administered as a 1000 mg/m2 IV infusion once daily for up to 5 days, depending on the assigned cohort (Fig 1). The starting cohort was Cohort 3 (CHOP + 1000 mg/m2 of daily belinostat on Days 1-3). Patients received primary prophylaxis with growth factor (G-CSF) support. Dose-limiting toxicities (DLT) were considered during the 1st cycle and included: non-hematological toxicity Grades 3-4, platelet count &lt; 25 X 109/L at any time or ANC &lt; 0.5 X 109/L lasting more than 7 days despite G-CSF administration. The primary endpoint of the study was the determination of the MTD of the Bel-CHOP combination. Secondary endpoints included safety, tolerability and ORR (complete response [CR] + partial response [PR]) and pharmacokinetics. Results: A total of 23 patients were enrolled in the study, 11 of which were treated in Part A. One patient in Part A was deemed inevaluable because the patient died due to disease progression before completing Cycle 1. The MTD was determined to be 1000 mg/m2 on Days 1-5 (Cohort 5); 12 more patients were then treated at this dose level (Part B). The only DLT experienced in the study was in Cohort 3 (Grade 3 Nausea and Vomiting). At the time of this abstract, 18/23 patients (78%) have completed all 6 cycles of Bel-CHOP, with 87% completing at least 4 cycles. Ten patients (43%) had at least one serious adverse event (SAE) and 18 (78%) had at least one Grade 3 or 4 adverse event (AE). The most frequent Grade 3/4 AEs were hematological in nature: neutrophil count decreased (26%), anemia (22%), neutropenia (17%) and white blood cell count decreased (17%). The ORR for the18 patients that have completed an End of Study Visit is 89% (16/18), with the vast majority achieving a CR [72% (n=13)], and 17% (n=3) a PR. Progressive disease was reported in 2 patients. Conclusions: These results demonstrate that the combination of belinostat with CHOP (Bel-CHOP) is well tolerated, with all components of CHOP and belinostat being given at their standard therapeutic doses. The rates of AEs were consistent with those typically reported with CHOP alone, and clinical activity was demonstrated with a response rate of 89% based on 18 evaluable patients. Thus, Bel-CHOP is a promising new regimen in PTCL that will be further tested in a Phase 3 randomized trial. Table. Table. Figure 1. Summary of Demographic and Baseline Characteristics AITL= angioimmunoblastic T-cell lymphoma; ALCL =anaplastic large-cell lymphoma; ALK = anaplastic lymphoma kinase; NOS = not otherwise specified Figure 1. Summary of Demographic and Baseline Characteristics. / AITL= angioimmunoblastic T-cell lymphoma; ALCL =anaplastic large-cell lymphoma; ALK = anaplastic lymphoma kinase; NOS = not otherwise specified Disclosures Barta: Seattle Genetics: Research Funding. Bhat:Spectrum Pharmaceuticals, Inc: Employment. Song:Spectrum Pharmaceutical, Inc: Employment. Choi:Apectrum Pharmaceuticals, Inc: Employment. Allen:Spectrum Pharmaceuticals, Inc: Employment. Foss:Spectrum Pharmaceuticals; Celgene: Seattle Genetics: Infinity; Millenium: Consultancy, Honoraria, Research Funding, Speakers Bureau.