Nageswara, Amulya A.

Abstract Background: Pediatric Anti-Phospholipid Syndrome (APS) is the most commonly acquired state of hypercoagulability in children, and is defined by venous and/or arterial thrombosis in the presence of circulating anti-phospholipid antibodies (aPLs) (most commonly lupus anticoagulant (LA), anticardiolipin antibody (aCL) and anti-β2-glycoprotein antibody (aβ2GP)). Catastrophic APS (CAPS) is a rare manifestation of APS, with thrombosis of multiple vessels that can lead to multi-system organ failure. Purpose: To determine the thromboses outcomes and factors predisposing to the risk of thrombotic recurrence in pediatric patients with a diagnosis of APS. Methods: Retrospective review of patients between the ages of 0-21 years diagnosed and treated with APS from 1997-2013 at our institution. Clinical data and long-term outcomes of these patients were reviewed. Exclusion criteria included neonatal APS and thrombosis with fetal loss. Statistical tests were performed using JMP software (© 2014 SAS Institute Inc., North Carolina, US). Associations between categorical variables were tested using chi-square test or Fisher’s exact test when required. Differences were considered statistically significant if p<0.05. Results: The study identified 23 patients (12 female; 11 male). Three patients with CAPS were identified and excluded from the analysis (3 female). Gender distribution for primary and secondary APS was similar (5 female/6 male primary APS; 4 female/5 male secondary APS). The median follow up period was 3.2 years (range; 0.01 – 16.87 years ). Median age at diagnosis of first episode of thrombosis was 16.16 years (range; 6.05 – 20.6 years). Nine patients (45%) with secondary APS had underlying autoimmune disease or malignancy (7 systemic lupus erythematosus, 1 ulcerative colitis, 1 Non-Hodgkin Lymphoma) and the remaining 11 patients were diagnosed as primary APS. Arterial and venous thrombosis occurred as the first thrombotic event in 7 (35%) and 13 (65%) patients, respectively. Lower extremity deep vein thrombosis (DVT) was the most frequent thrombotic event 11/20 (55%), followed by pulmonary embolism 7/20 (35%), ischemic stroke 4/20 (20%), lower extremity arterial thrombosis 3/20 (15%), upper extremity DVT 2/20 (10%), and IVC thrombosis 2/20 (10%). Recurrent or progressive thrombotic events occurred in 12/20 patients (60%). Of those, 7 were venous (58%), 5 were arterial (42%). At the time of recurrence, 3 patients were fully anticoagulated, (INR 2.5-3.5) versus 9 who were subtherapeutic (INR<2.0). Recurrent/progression thrombotic events occurred at the original site of thrombosis in 8 patients (3 arterial, 5 venous) while the remaining 4 recurrent thrombotic events occurred at other sites than the primary site. Overall venous and arterial thrombotic events were no different among primary or secondary APS (p=0.88). Thrombosis recurrence/progression risk at the original site or distant site was no different among primary or secondary APS (p=0.22 and p=0.30 respectively). Risk of recurrence/progression was not associated with subtherapeutic levels of anticoagulation (p=0.08), or presence of residual thrombosis at primary site at the time of recurrence (p=0.48). Conclusion: Recurrence and/or progression of thrombosis in APS occurred in 60% of the patients in our cohort, with 25% of the thrombosis recurrences occurring despite documented therapeutic anticoagulation in these patients. In contrast to other studies, our APS cohort demonstrated a higher rate of recurrence with other groups reporting thrombosis rates of recurrence such as 19-25%. Our cohort demonstrated similar rates of primary and secondary APS among female patients, in contrast to other studies suggesting higher rates of secondary APS in females. Potential risk factors such as primary versus secondary APS, subtherapeutic anticoagulation, and residual thrombosis from primary thrombotic event were not found as significant risk factors for thrombosis recurrence. Larger pediatric APS studies are needed in order to address other potential risk factors for thrombosis (ie obesity, inherited thrombophilia, intensity of anticoagulation, immune suppression approach for secondary APS), in order to establish treatment strategies for the prevention of recurrent thrombosis. Disclosures No relevant conflicts of interest to declare.

Abstract Abstract 4651 Introduction Graft versus host disease remains a major cause of mortality and morbidity following matched unrelated hematopoietic stem cell transplantation. Campath-1H (Alemtuzumab) is a humanized monoclonal antibody to CD52, an antigen expressed on T and B lymphocytes, monocytes and natural killer cells and is thought to reduce GVHD incidence through in vivo T cell depletion. Through the same mechanism it can potentially increase the risk of relapse by reducing the graft vs. leukemia effect and also possibly increase the risk of infection due to delayed immune recovery. This study looks at our experience with Campath-1H substituted in place of the conventional anti-thymocyte globulin (ATG) in our transplant conditioning regimen. Patients and Methods This retrospective case study included 17 pediatric (9 male; 8 female) matched unrelated bone marrow transplants done in our institution between January 2003 and June 2009 with Campath-1H as part of the pretransplant conditioning regimen. The primary transplant indication was leukemia/lymphoma (n=9), MDS/ MDS evolving into AML (n= 3), severe aplastic anemia (n=4) and Fanconi anemia (n=1). The conditioning regimen included Campath-1H given with cytoxan/ total body irradiation (TBI) in 14 patients, fludarabine/ TBI in 2 patients, and melphalan/ fludarabine in 1 patient. Campath-1H dosing was body weight based: 3mg (if between 5-15kg), 5 mg (if between 16-30kg) and 10 mg (if >30 kg) and 3 doses were administered when underlying condition was a malignancy and 4 doses when it was a bone marrow failure state. The last dose was given at least 24 hours prior to the bone marrow/ peripheral stem cell infusion. GVHD prophylaxis was with tacrolimus/methotrexate (n=12), tacrolimus (n=4) and cyclosporine/methotrexate (n=1). Standard institutional infectious prophylaxis was followed. Results The median age at transplant was 12.2 years (range; 0.7-19.7 years). All but one patient engrafted with a median of 21 days (range; 14-25 days). 5 out of 17 developed Grade I-II acute GVHD which resolved with steroids. No patient developed chronic GVHD. One patient had a CMV reactivation but no patient developed active CMV disease. 4 patients had varicella one of whom died of disseminated infection (day +376). The same patient also had adeno viral infection and BK viremia. 1 patient developed PCP pneumonia and retinal toxoplasmosis. 5 patients (6 transplants) relapsed (range; 40-641 days) with 3 relapsing within +100 days. 1 patient developed PTLD which was successfully treated with rituximab. Of the 4 patient deaths 3 were due to relapse and one due to disseminated varicella infection. The median follow-up time was 719 days (range; 147-2175 days). Overall survival as calculated using the Kaplan-Meir analysis was 100 % at 100 days and 94% at 1 year. Event free survival censoring for death, relapse and rejection was 76% at 100 days and 64% at 1 year. Conclusions Based on our experience, Campath-1H used as part of pretransplant conditioning regimen in pediatric matched unrelated transplants seems to reduce the risk of serious GVHD. This is in concordance with other published literature. T cell depletion is considered to increase the risk of life threatening infections. Our study had one infection related death. There were no patients with active CMV disease. This may in part be attributed to strict prophylactic measures and increased surveillance. Longer duration of follow-up is required to adequately analyze the relapse rates. Also, given our small patient numbers the effect of primary disease state and stage on relapse could not be assessed. Larger studies in the pediatric population with longer duration of follow-up comparing Campath-1H with conventional regimens are required to further assess its role with regards to graft vs. leukemia effect and also to establish if the decreased incidence of GVHD is sustained in larger cohorts. Disclosures: No relevant conflicts of interest to declare.