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Opposing acute lymphoblastic leukemia, sparse data about AYAs with acute myeloid leukemia (AML) is available. Overall, 125 AYAs (age 10-35 years) treated during the last two decades were evaluated and compared to 385 older patients. CBF leukemia was more frequent in AYAs (21.6% vs. 8%

Introduction Anti-thymocyte globulin (ATG)-based immunosuppressive therapy is often used in allogeneic hematopoietic cell transplantation to reduce incidence and severity of graft-versus-host disease (GVHD). Patients and Methods In our observational study, ATG (rabbit, Thymoglobulin; Sanofi, 5 mg/kg) was administered as a standardized part of the conditioning in 97 patients with a median age of 34 years (range, 14-58 years), allotransplanted for hematologic malignancies from matched (8/8; n = 52) and allele or antigen mismatched (7/8; n = 43 and 6/8; n = 2) unrelated donors. Results Five-year overall survival (OS) was 46.9%, disease-free survival was 46.5%, and treatment-related mortality was 20.6%, with a median follow-up of 29 months (range, 1-145 months). Acute GVHD (grade ≥ II) cumulative incidence was 26.9% in matched versus 50.5% in mismatched patients ( P = .060), whereas extensive chronic GVHD was 45.6% versus 50%, respectively ( P = .310). Five-year OS was 62.2% for the matched patients and 27.9% for the mismatched patients ( P = .003) owing to a higher treatment-related mortality rate in mismatched patients ( P = .032). In multivariate analysis including age, gender, time until transplantation, disease phase, mismatched donor, ABO mismatch, number of CD34+ infused, acute and chronic GVHD, the significant unfavorable factors for OS were HLA mismatch and advanced disease phase. Conclusion A relatively low-dose ATG is effective in acute GVHD prophylaxis, leading to promising survival rates in matched transplants. Further comparative studies with adjusted ATG dose depending on Human leukocyte antigen disparity or alternative donors are warranted.

ADAMTS13 (A Disintegrin and Metalloprotease with ThromboSpondin type 1 motifs) activity is a key tool in differential diagnosis of thrombotic microangiopathies (TMAs). Due to the lack of availability of ADAMTS13 testing, PLASMIC/PLASIC scores have been suggested to predict ADAMTS13 deficiency. The importance of differentiating TTP from other complement-mediated TMAs is highlighted by the need to urgently start plasma exchange and utility of treatments such as caplacizumab or eculuzimab. Therefore, we aimed to evaluate ADAMTS13 activity, PLASMIC/PLASIC scores, and complement testing in guiding management of a real-world TMA cohort. We enrolled consecutive TMA patients with samples referred to our Center (01/2018–2020). If ADAMTS13 ​> ​10%, soluble C5b-9 was measured. Among 80 TMA patients, ADAMTS13 activity was ≤10% in 50 patients, while 28 had a relapsing disease. PLASMIC/PLASIC were excellent predictors of ADAMTS13 deficiency, especially in patients without secondary causes. Soluble C5b-9 levels were elevated (median 525 ​ng/ml, range 313–913 ​ng/ml) in 7 patients without secondary causes and ADAMTS13 ​> ​10% (hemolytic uremic syndrome/HUS). Two were shiga-toxin associated; while 5 atypical HUS. Only 1/5 patients received eculizumab and achieved TMA resolution implemented by guidance based on soluble C5b-9 levels. In transplant-associated TMA, 8/16 patients not responding to first-line treatment received eculizumab due to elevated C5b-9 levels (median 353 ​ng/ml, range 281–1252 ​ng/ml) and achieved TMA resolution. In conclusion, our real-world data confirm that ADAMTS13, complement testing, and PLASMIC/PLASIC are valuable tools in diagnosis and management of TMAs, but also highlight the unmet need of using available markers and treatments in clinical practice.

Introduction: ADAMTS13 (A Disintegrin and Metalloprotease with ThromboSpondin type 1 repeats) activity remains a key tool in differential diagnosis of thrombotic microangiopathies (TMAs). However, ADAMTS13 testing is not readily available in many hospitals. Recently, PLASMIC and PLASIC scores have been developed to facilitate rapid recognition of TTP. We aimed to evaluate their usefulness compared to ADAMTS13 testing in a real-world cohort of TMA patients. Methods: We enrolled consecutive patients with samples referred to our Center for ADAMTS13 measurement due to TMA over the last 2 years. Samples were collected either at first diagnosis or relapse before initiation of treatment. ADAMTS13 activity was measured with a commercially available and validated ELISA kit (Technozym, Diapharma). Clinical data were retrospectively collected from referring centers. Management was based on treating physicians' decisions. TTP was defined as severe ADAMTS13 deficiency (activity≤10%); while secondary TMAs were diagnosed in patients with cancer, connective tissue disorders or hematopoietic cell transplantation recipients (transplant-associated TMA). Atypical hemolytic uremic syndrome (aHUS) remained a diagnosis of exclusion in patients with ADAMTS13>10%. PLASMIC was calculated based on seven variables: platelets, hemolysis, cancer, transplant, MCV, INR, creatinine; while MCV was not included in PLASIC, as previously described. ROC curve analysis was performed to determine the sensitivity and specificity of scores. Multivariate binary or logistic regression models were performed when appropriate. Results: We studied 50 TMA patients. Combined clinical and laboratory data conferred the following TMA classification: TTP in 36 patients (72%), transplant-associated TMA in 7 (14%), other secondary TMA in 5 and aHUS in 2. PLASMIC score was intermediate in 2 and high in another 4 patients without TTP. The PLASIC score was high in 5 patients without TTP, leading to less false positive results compared to PLASMIC (p Plasma exchange was commenced in the majority of patients (42/50, 84%). Among TTP patients, the majority (77%) received rituximab as salvage or prophylactic treatment. Rituximab administration was associated with platelet (p=0.003) and ADAMTS13 (p=0.015) levels at diagnosis. The complement inhibitor eculizumab was administered in 3 patients with TA-TMA, who achieved TMA resolution. With a median follow-up of 2.9 years (range 0.3-26.3), overall survival was significantly lower in patients with secondary TMAs (p Conclusion: PLASMIC and PLASIC scores are excellent tools in TMA patients without secondary causes. While PLASMIC and PLASIC scores conferred similar outcomes, the PLASIC score requires six instead of seven variables, is classified as low/high omitting the intermediate category and leads to less false positive results. Further validation of the PLASIC score might confirm its clinical value. In addition, the role of ADAMTS13 levels in guiding rituximab administration needs to be further investigated. When an underlying etiology is detected, ADAMTS13 testing is necessary to exclude TTP and facilitate further therapeutic decisions. Figure 1 Disclosures Panayiotidis: Bayer: Other: Support of clinical trial.

Monosomal karyotype (MK) has recently been reported to identify a distinct subset of acute myeloid leukemia (AML) with adverse prognosis. We retrospectively evaluated the frequency of MK in a large cohort of 549 unselected AML cases diagnosed in our department over a period of 13 years and explored potential associations with clinicobiological features and outcome. MK was found in 62 of 549 cases (11.3%), with all but one assigned to the unfavorable cytogenetic risk category; 57 of these 62 MK cases had a complex karyotype. Comparison with a subgroup of AML cases, who had unfavorable karyotypic profiles yet without MK (non-MK) and who were treated uniformly with similar, "3+7"-based regimens, revealed significant (P0.05) associations between MK and advanced age, low white blood cell count at diagnosis, and inferior overall survival (6.5 vs. 15 months for non-MK cases). In conclusion, MK defines a sizeable subset of patients with unfavorable cytogenetics who exhibit a distinct clinical profile, even in direct comparison with other unfavorable karyotypes.

Background: Infections are a leading cause of morbidity and mortality in patients suffering from hematological malignancies, with resistant bacteria being a major contributor. Special precaution is needed in these patients due to immunosuppression and safety measures are warranted to reduce related complications. Surveillance studies can offer a better understanding of risk factors associated with resistant strains and mortality. Materials and Methods: All patients hospitalized in our department of hematology, hematopoietic stem cell transplantation (HSCT) and post-transplant unit during 2014 and 2015 who presented an infectious episode were included in our study. An infectious episode was defined as a clinically detected infection not necessarily associated with specific bacteria or a positive surveillance culture. A retrospective epidemiological study was conducted using clinical data and positive cultures along with information about resistance. Our goal was to explore risk factors for infections by resistant bacteria and examine the impact of resistance on mortality. Results: During the two-year period, we identified 439 infectious episodes, 55.4% deriving from the department of hematology and 44.6% from the HSCT and post-transplant unit. Hematological malignancy was diagnosed in 429 patients, with 62.2% suffering from acute leukemia. Prevalence of resistant bacteria in our study population was 37.1%, more frequently isolated in the HSCT and post-transplant unit (52.2% vs 34.7%, p=0.001). Most of them were gram-negative, with the main representative being KPC klebsiella pneumoniae (38.7%), followed by pseudomonas aeruginosa (17.2%). Gram-positive species accounted for 19% of resistant bacteria, including MRSA staphylococcus and VRE enterococcus species. During the first semester of 2014, we identified a burkholderia cepacia outbreak with a total of 13 cases, that was successfully handled and the microorganism was eradicated. Possible risk factors for the isolation of resistant bacteria were examined. Factors included in our analysis were diagnosis, department of hospitalization, transplantation, prior chemotherapy, the presence of central venous catheter (CVC) and the presence of neutropenia. In multivariate analysis, the only significant risk factor associated with isolation of resistant bacteria was the department of hospitalization (OR 2.57, CI 1.31-5.02, p= 0.006). Duration of neutropenia was not correlated with increased rates of antimicrobial resistance (p=0.91). Mortality rate was 5.2%, mostly related to infection. Of the 23 patients that died, only six deaths were attributed to refractory disease. However, from the remaining 17, we identified 7 who presented severe immunosuppression after transplantation due to graft versus host disease (GVHD). Mortality was increased in patients with isolation of a resistant strain (73.9% vs 26.1%, p=0.001) but was not related to resistant disease or in combination with GVHD (52.9% vs 50%, p= 0.9). Using multivariate analysis, significant factors predicting mortality were neutropenia, the presence of resistant bacteria and presence of CVC. Other factors included in our analysis were the department of hospitalization, transplantation, diagnosis and preceding chemotherapy. The most powerful factor was the isolation of resistant bacteria (OR 4.08, CI 1.48-11.25, p=0.006) followed by the presence of CVC (OR 3.78, CI 1.14-12.54, p=0.03). Finally, we compared the impact of resistant bacteria between 2014 and 2015 and we observed a significant reduction in 2015 (57.1% vs 33.9%, p Conclusion: From our study we can conclude that patient colonization and possibly personnel behavior play a significant role in spreading of resistant bacteria, as the department of hospitalization was the only significant factor of bacteria isolation. Our two departments are localized in different floors of the same building with different staff on each floor, which makes cross contamination difficult. Resistance has a major impact on mortality, but appropriate measures can change distribution and improve survival in patients with hematological malignancies. Disclosures No relevant conflicts of interest to declare.

Background The case of a male patient, 25, who presented with pleural effusion. Further imaging examinations demonstrated mediastinal and cervical lymphadenopathy.

Abstract 3596 Immune phenotyping plays a critical role in the diagnosis and classification of acute leukemia. Several studies have reported a variable proportion of patients with acute myeloid leukemia (AML) expressing lymphoid-associated antigens (LAA). The exact frequency and true clinical significance of this phenomenon remains undefined due to inconsistencies between series, likely related to methodological aspects or potential case selection biases. We retrospectively evaluated the expression of LAA in blast cells from 278 consecutive and unselected patients with AML diagnosed in our Department between 2002 and 2010. The patient cohort included 168 males and 110 females with a median age of 61 years (range, 10–88); 146/278 cases were above the age of 60. Within this cohort, 190 cases (68%) had de novo AML, whereas the remaining 88 cases (32%) concerned secondary AML (sAML) to either MDS (n=80) or other non-hematologic malignancies (n=8). Patients were treated uniformly according to age with Aracytin/Idarubicin induction regimens (“3+7” or “2+5” for ages \q60 or ≥60, respectively). The immunophenotype was determined by flow cytometric analysis of (mainly) bone marrow aspirate and/or peripheral blood samples utilizing a primary CD45/side scatter (SSC) gating procedure with antibodies against CD7, CD13, CD19, CD33, CD4, CD10, CD34, CD117, CD64, HLA-DR, CD20, CD2, CD15, CD56, CD14, CD8, MPO, CD3, CD79a, CD22, TdT and lysozyme; a cut-off value for positivity of 20% was adopted. Overall, we identified 153/278 cases (55%) expressing at least one LAA. The most commonly expressed LAAs were CD4 (outside AML with monocytic differentiation), CD56, CD7, CD2, CD10 and CD79a (in 39%, 33%, 29%, 14%, 10% and 8% of LAA+ AML cases, respectively); interestingly, all CD79a-positive cases co-expressed at least one more LAA. A significant association was identified between LAA expression and cytogenetic profile: in particular, at least one LAA was detected in 37/50 cases (74%) with adverse cytogenetics (SWOG unfavorable and/or monosomal karyotype), compared to 24/41 (58%) cytogenetically favorable cases and 68/134 (51%) cytogenetically intermediate risk cases (p=0.01). No other statistically significant associations were found for LAA expression (positive vs. negative) in respect to age and complete remission (CR) rate. Furthermore, the frequency of LAA-positive cases was identical (55%) in both de novo AML (105/190 cases) and sAML (48/88 cases). Monoparametric statistical analysis was also performed individually for each of the six more frequent LAAs. Significant associations (p Disclosures: No relevant conflicts of interest to declare.

Abstract 4567 Background: Allogeneic hematopoietic cell transplantation (alloHCT) is a potentially curative treatment for patients (pts) suffering of AML with high risk features at diagnosis and beyond 1st complete remission (CR1) it remains the sole rescue treatment. In this retrospective study we analysed the data of all pts (149) allografted concecutively in our BMT unit for AML from 1991 to 2009. The aim of the study was to estimate the outcome in terms of overall survival (OS), disease free survival (DFS), relapse rate (RR) and non relapse mortality (NRM). Sixty-three pts of a median age 35 (8-63) years suffered from de novo (58), secondary (4) and biphenotypic AML (1) were transplanted in CR1. Cytogenetic analysis was available in 40/63 pts (intermediate 32, poor risk 8). Donors were siblings in 55, relative (1 antigen mismatch) in 3, unrelated (4 mismatched with 1–2 alleles) in 8 pts. Graft source was bone marrow (BM) in 12 and peripheral blood (PB) in 51 pts. Fifty-six received a myeloablative (MA) and 7 non- myeloablative (NMA) conditioning regimen. Eighty-six pts were allografted beyond CR1. Disease status was primary refractory (Prim. Ref) in 42/86, CR2 in 15, 1st refractory after re-induction relapse (Rel1) in 23 and advanced (CR3; Rel2+) in 6 pts. Three pts were retransplanted from the original donor for relapsed disease after alloHCT. In the cohort of pts with disease beyond CR1, cytogenetic analysis was available in 71 (favourable 4, intermediate 53, poor risk 14). Donors were siblings in 58, syngeneic (1 antigen mismatch) in 8, unrelated (3 with mismatch) in 17, unrelated double cord blood (CB) in 1, haploidentical in 5 pts. The majority of the pts received mobilized PB (72) as graft source and myeloablative conditioning regimen (82). Results: For pts transplanted in CR1 OS was 63%, NRM 23%, DFS 60% and RR 21% at 13 years. Seventeen pts transplanted before 2000 had an estimated OS and DFS 59%, RR 9% and NRM 35% whereas for forty-six pts transplanted after 1999 the OS was 64%, DFS 61%, NRM 17% and RR 25% at 9 years. DFS for pts in CR1 with an unrelated donor was 47% and 62% for siblings. Myeloablative regimen resulted in 65% DFS while NMA in lower DFS (21%) due to higher RR. According to cytogenetics OS and DFS were 62% and 64% for the intermediate risk group (n=32), 44% and 45% for the poor risk (n=8) respectively. For the cohort of pts transplanted for Prim. Ref. disease (n=42) OS was 20% (plateau at 3 years), DFS 17% (plateau at 2 years), RR 78% and NRM 34% at 12 years. Despite the small number of pts with poor risk karyotype (n=7) the prognosis seemed to be dismal (DFS and OS 0%) versus 25% and 31% respectively for the intermediate risk group (n=28). For pts transplanted in CR2 (n=15) OS was 51% and DFS 46% (plateau at 1year), RR 43% and NRM 16%. For pts in REL1 (n=23) OS was 15%, NRM 56%, DFS 4% and RR 86%. For the 6 pts transplanted for advanced disease (CR3; REL2+) OS was 17%, DFS 17%, RR 67% and NRM 50%. The 5 pts undergone haploidentical alloHCT (2 Prim. Ref., 2 CR2, 1 CR3) after TBI 8/thiotepa/fludara/ATG had OS and DFS 40% at 8 years. One of 3 pts retransplanted is alive in CR and the rest succumbed to their disease. Discussion: In 2010 when the use of alternative transplantation has been expanted the selection of pts upon the best stratification and the timing of the transplantation still remain open questions. The majority of patients are classified in the intermediate risk group with normal karyotype. According to our experience during the last two decades alloHCT for AML in early disease phase (CR1) can offer the best results and possibly cure in a significant number of patients (60%). Transplantation procedures have been continuously improved over time leading to improvement of the outcome mostly in the era of alternative donor alloHCT. For poor risk pts in CR1 and for all pts with AML beyond CR1 (apart from acute promyelocytic leukemia in molecular remission) alloHCT remains the only treatment option. In this cohort of pts results from our data indicate that pts in CR2 may attain long term survival after alloHCT (OS 51%, NRM 16%). Among pts refractory to induction and salvage treatment therapies (> CR2, Prim Ref., REL) a small proportion of pts (15-20%) may be rescued by alloHCT. Disclosures: No relevant conflicts of interest to declare.