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Abstract Background: Acute myeloid leukemia (AML) is an aggressive blood cancer with a wide range of response and relapse rates using standard chemotherapy combining anthracycline plus cytarabine (7+3). The stem cell receptor tyrosine kinase KIT is expressed on more than 10% of blasts in 95% of relapsed AML cases and mediates leukemic proliferation and has anti-apoptotic effects (Domen and Weissman 2000). AML with high KIT expression is associated with poorer outcome (Del Poeta, Venditti et al 2003). Goals: To study the efficacy and safety of combination 7+3 and nilotinib in patients (pts) with AML and KIT expression. Primary goal is to determine the complete response (CR) rate; while secondary goals include 2-year overall survival (OS) and disease free survival (DFS) in addition to safety. Methods: A single arm, Phase II study, enrolled pts at Mayo Clinic (MN and AZ). Appropriate IRB was obtained and study was registered (NCT 01806571). Pts were enrolled if they were newly diagnosed with AML with KIT (CD117) expression of ≥ 20% on myeloblasts by flow cytometry. KIT mutations were allowed. Nilotinib 300 mg twice daily was given on days 4-14 of induction and consolidation; and continuous daily maintenance therapy for up to 2 years. Cytarabine 100 mg/m2/day continuous IV x7 days plus daunorubicin 60 mg/m2 IV daily x3 days were used for induction, while consolidation used standard cytarabine 3 gm/m2 twice daily days 1, 3, 5 for a total of 4 cycles. This is a Simon 1-stage design with a safety analysis after enrolling 12 pts, and an interim analysis after enrolling 18 out of 43 pts (Al-Kali, ASH 2015) recommended to continue study accrual. Results: i)- Demographics: Thirty four pts were enrolled from July 2013 to June 2017. Median age was 59 years (range 24-69) with 71% being male. Median laboratory findings include hemoglobin of 8.8 gm/dL, platelets of 56 x109/L, white blood count of 3.3 x109/L (0.4-125), and peripheral blood blasts 17 %(0-94%). Cytogenetics were normal in 43% of the pts and favorable cytogenetics were seen in 6%(inv 16). FLT3 gene testing was done on 26 pts and was positive in 13%. KIT gene sequencing (exon 8, 9, 10, 11, 17) revealed pathogenic mutation in 1/28 cases (4%). ii)- Clinical outcome Out of all 34 pts enrolled on the study, 18 (53%) achieved CR (or CR with incomplete platelet recovery) with a median CR duration of 21.8 months. Of 26 evaluable pts, the overall CR rate was 69%. 4 of the 18 pts (22%) who achieved remission needed a second induction. One pt died due to liver failure (had only one dose of nilotinib and toxicity was attributed to daunorubicin). 13 (38%) pts proceeded to allogeneic stem cell transplant (HSCT), 12 of whom are alive and none were able to initiate nilotinib maintenance. Only 6 (1 had HSCT) out of 34 (18%) pts relapsed after achieving CR. Median DFS was 45.8 months, while median OS was 42.4 months. 2-year DFS and OS were 58% and 72%, respectively. iii)- Safety Thirty four pts were evaluated for adverse events (AE). Fourteen pts had G4 non-hematological AEs, including fourteen G4 AEs related to infection, 2 with electrolyte imbalances, 1 heart failure, 1 elevated bilirubin, 1 elevated lipase, and 1 jejunal hemorrhage. One patient had G5 liver failure. Most common (>20%) G3 non-hematological AEs were febrile neutropenia (56%), hypophosphatemia (21%), elevated ALT (21%) and hypertension (21%). Conclusion: Combination daunorubicin and cytarabine with nilotinib (DATA) appears to be safe and effective. Final results show an acceptable safety profile with most common AE being infection. Thirty day mortality was low (3%). DATA regimen has comparable CR rates of 53% (intent to treat) and 69% in evaluable pts. Relapse rates were very low at 18% with durable responses and encouraging survival rates. Figure. Figure. Disclosures Al-Kali: Novartis: Research Funding. Tibes:Novartis: Research Funding. Palmer:Novartis: Research Funding.

Abstract Background Current literature suggests that the presence and quality of social support may provide meaningful benefits in overall survival of HCT recipients. Further, studies in general oncology and renal transplantation population suggest that married patients have favorable outcomes. Caregivers of HCT recipients are an important source of both instrumental and emotional support, and a reasonable surrogate for presence of social support. Using data from Center for International Blood and Marrow Transplant Research (CIBMTR), we examined the potential influence of marital status (surrogate for caregiver) at the time of HCT on outcomes of HCT. Methods Patients, >40 years of age who underwent either autologous or allogeneic-HCT from 2008 to 2015 were included. Marital status was defined as either 1) Married, 2) Single, never married, 3) Separated/divorced, and 4) Widowed. The probability of OS at 5 years, Grade 2-4 acute GVHD at 100 days and chronic GVHD at 2 years were estimated as appropriate using the Kaplan-Meier method with the log-rank test used for univariate comparisons. Multivariate analysis was performed to determine the association of marital status with these outcomes, while adjusting for clinical and sociodemographic variables. Results We identified 10,226 allogeneic and 5,714 autologous HCT patients; the median follow-up of survivors was 37 months (range 1-102 months) and 40 months (range 1-106 months) respectively. In the allogeneic population, there were n=7,999 married, n=741 single, n=1,175 separated/divorced and n=311 widowed patients. There were n=4,308, n=478, n=695 and n=233 respectively in the autologous population. The baseline characteristics amongst the 4 groups of marital status were comparable. In the allogeneic population, the 5-year probability of OS, 100-day Grade 2-4 acute GVHD, 2-year probability of chronic GVHD were 38% [95%CI (36-39%)], 16% [95%CI (15-17%)]and 46% [95%CI (45-47%)] respectively; while the 5-year probability of OS in the autologous population was 63% [95%CI (61-64%)]. When compared with married patients, single, separated/divorced and widowed patients were not at an increased risk of death [HR 1.09, 95%CI (0.98-1.2); HR 1.01, 95%CI (0.93-1.09); HR 1.09, 95%CI (0.98-1.2)] in the allogeneic setting. Similarly, there was no association of marital status and OS in the autologous setting [HR 1.10, 95%CI (0.92-1.33); HR 1.17, 95%CI (1.01-1.36); HR 1.08, 95%CI (0.86-1.37)] respectively. In contrast, marital status in the allogeneic setting was associated with an increased risk of grade 2-4 acute GVHD in patients who are divorced/separated as compared to married patients [HR 1.13, 95%CI (1.03-1.24)] but not chronic GVHD [HR 0.90, 95%CI (0.80-1.02); HR 0.94, 95%CI (0.86-1.04); HR 0.82, 95%CI (0.68-0.99)] respectively. We did not identify an interaction between marital status and gender. Conclusions Our data suggest the marital status in patients undergoing either autologous or allogeneic HCT is not associated with overall survival or chronic GVHD, while the risk of acute GVHD maybe increased in patients who are divorced/separated. Taken together, the effect of marital status on post-HCT outcomes is negligible when other patient, disease and transplant variables are considered. Alternatively, marital status maybe an imperfect marker for positive social support. Future research should consider measuring social support using validated scales and assess health related quality of life together with health care utilization outcomes to better appreciate the potential impact of social support. Disclosures No relevant conflicts of interest to declare.

Abstract Background Predictors of outcomes after reduced intensity conditioning (RIC) stem cell transplantation (SCT) in chronic lymphocytic leukemia (CLL) are not well established. The Dana Farber (DF) investigators (Brown et al, leukemia 2013) developed a prognostic scoring model for overall survival (OS) and disease free survival (DFS) that assigned one point to each of comorbidity index, absolute lymphocyte count, LDH and disease status. The goals of the present study were to 1) validate the DF model 2) identify additional predictors of outcomes after SCT. Methods This study is a retrospective review of the Mayo Clinic CLL database and was approved by the Institutional Review Board. All CLL patients that underwent RIC-SCT were included. The prognostic significance of prognostic factors at time of RIC-SCT were analyzed, including the DF model. Survival was estimated and compared using the Kaplan Meier and Log Rank tests. Results From 2006 to 2012, 50 patients with CLL underwent RIC-SCT at the Mayo Clinic. Of these, 33 were male (66%) and the median age was 56 (29-69) years. The median time from diagnosis to RIC-SCT was 4.7 years (0.6-22.9). Indications for RIC-SCT were 17p deletion in 24 (48%) patients and purine nucleoside analogue (PNA) refractory disease in 26 (52%) patients. Transplant related mortality was 6% and non-relapse mortality at 5 years was 14%. Acute graft versus host disease (GVHD) developed in 30 (60%) patients and chronic (c) GVHD was noted in 32 patients (64%). The 5-year relapse rate was 38%. The DF prognostic score stratified three categories for OS (score of 0, 1-2, ≥ 3), but was not associated with DFS in this cohort. We next evaluated the impact of other patient, disease, and transplant characteristics on clinical outcome. Development of cGVHD post-transplant was the dominant predictor of both DFS (HR 0.26, 95% CI=0.10-0.69, P=0.006) and OS (HR 0.04, 95% CI=0.01-0.19, P<0.0001, figure 1). The presence of 17p deletion at time of RIC-SCT was associated with shorter DFS (HR 3.99, 95% CI=1.43-11.18, P=0.008), but did not impact OS. Developing cGVH but not DF score remained an independent predictor of OS on a multi-variate analysis including both factors. Given these findings, we evaluated what pre-treatment patient, disease, and transplant characteristics predicted for subsequent development of cGVHD. Patients with higher scores on DF prognostic model were less likely to develop cGVHD (score 0=66%, 1-2=76%, ≥3=31%; P=0.01). Three CLL characteristics (complete or partial remission at time of RIC-SCT, absence of 17p deletion, and absence of ZAP70 overexpression) were predictors for development of cGVHD while alemtuzumab exposure ≤3 months prior to RIC-SCT decreased likelihood of cGVHD. On multivariate modeling using these four predictors, only ZAP70 overexpression was an independent negative predictor of developing cGVHD (Table 1). Rates of cGVHD post RIC-SCT in ZAP 70 positive and ZAP70 negative patients were 50% and 92%, respectively (p=0.03). Conclusion This study found that while the DF prognostic score is an effective way to predict outcome prior to RIC-SCT, development of cGVHD post-transplant is ultimately the most significant predictor for both OS and DFS after transplant in patients with CLL. Pretransplant characteristics that predict subsequent cGVHD include DF prognostic score and ZAP70 status. This is the first report to identify biologic characteristics of CLL B-cells associated with development of cGVHD post-transplant. 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 Allogeneic stem cell transplantation (allo-SCT) is a potentially curative option for patients with myelodysplastic syndromes (MDS). However, allo-SCT can be associated with significant morbidity and mortality along with a risk for post-transplant disease relapse. While many MDS prognostic models exist, a prognostic model specifically designed to predict post-transplant disease relapse is yet to be developed. Therefore, we carried out this single institution study. Methods After due IRB approval, the Mayo Clinic MDS database (1995-2012) was retrospectively reviewed. This database contains comprehensive information on MDS clinical and pathological characteristics, treatments and SCT. Primary outcomes analyzed included disease free survival (DFS), overall survival (OS) and relapse rates at five years post allo-SCT. In addition, we evaluated transplant related mortality (TRM), non-relapse mortality (NRM), and rates of acute and chronic graft versus host disease (GVHD). DFS and OS were calculated from the time of transplantation. The prognostic relevance of several disease and transplant specific characteristics were analyzed, including: age, gender, World Health Organization (WHO) categories, therapy related MDS, cytogenetics, International Prognostic Scoring System (IPSS) and IPSS-Revised (IPSS-R) at the time of MDS diagnosis, transfusion dependence, bone marrow and circulating blast count at transplant, serum ferritin levels, SCT Co-morbidity Index, donor source, HLA matching, CMV serostatus, and conditioning regimen. Multivariate analysis was performed using the Cox Proportional Hazard Model. Survival was estimated and compared using the Kaplan Meier and Log Rank tests, respectively. Results From 1995 through 2012, 96 consecutive patients with MDS underwent allo-SCT at the Mayo Clinic, Rochester. Of these, 62 were male (65%) with a median age of 54 (24-68 years). The median follow up was 31 (1-181) months. Twenty seven patients (28%) had therapy related MDS and 39 (40%) had MDS with a monosomal karyotype. IPSS-R risk stratification identified 55 (57%) patients with very high, 20 (21%) with high and 21 (22%) with intermediate/good risk disease. Fifty (52%) patients received a reduced intensity conditioning. The TRM was 8% and NRM at 5 years was 22%. Acute (grade 2 to 4) GVHD developed in 57 (59%) patients and chronic extensive GVHD was noted in 52 (54%) patients. Five-year relapse, DFS and OS rates were 24%, 42%, and 44%, respectively. In a univariate analysis, IPSS-R (high/very high, P=0.005), therapy related MDS (P=0.009), bone marrow blast count at transplant (≥10%, P=0.01), and the presence of a monosomal karyotype (P=0.05) were significantly associated with worse DFS. On a multivariable analysis, only high or very high risk IPSS-R category (HR 7.8, P=0.005) and therapy related MDS (HR 3.9, P=0.04) retained their negative prognostic impact. Based on this finding, we developed a prognostic model that assigned one point to each of these two factors (low risk-0, intermediate-1 and high risk-2). This model successfully stratified patients based on DFS, with a 5-year DFS of 67%, 40% and 23% for low, intermediate and high risk categories respectively, P=0.0012. This model was also successful in risk stratifying patients with regards to OS (table 1, figure 1). The presence of chronic GVHD was associated with a significantly improved DFS (62% vs 24%, P<0.0001) and OS (78% vs 19%, P<0.0001), however, as this is a post-transplant outcome, it was not included in the analysis/model. Conclusions Although the IPSS-R has not been validated in therapy related MDS or in patients who have received MDS directed therapy, the high/very high risk categories along with therapy related MDS, serve as independent predictors of OS and disease relapse after allo-SCT. Using these two variables, our prognostic model efficiently stratified patients with regards to DFS, relapse rates, and OS. Given the smaller sample size validation in a larger patient cohort will be needed. Disclosures: No relevant conflicts of interest to declare.

Abstract Background Voriconazole is a common antifungal medication used in allogeneic hematopoietic stem cell transplantation (allo-HSCT) patients. In solid organ transplantation, multiple studies have associated the use of voriconazole with the development of squamous cell carcinoma (SCC) post-transplant, but its association with SCC in allo-HSCT patients is unknown. We sought to determine this association. Methods After IRB approval, Mayo Clinic’s transplant database (2007-2012) was accessed and electronic charts of allo-HSCT patients were retrospectively reviewed. Voriconazole exposure was defined as exposure to voriconazole at any time during treatment of primary disease, prior to or following HSCT. Cumulative voriconazole exposure was defined as total days of voriconazole use following HSCT; days were not required to be consecutive. Two time-dependent voriconazole exposure variables were defined: (1) history of voriconazole exposure (yes/no) over time, and (2) cumulative days on voriconazole over time. Results 404 patients underwent allo-HSCT during this timeframe, and 381 patients (table 1) were included in the final analysis. 23 patients were excluded (8 patients received multiple transplants, 9 patients were treated under pediatric protocols, 6 patients lacked research consent). 312/381 received voriconazole; other antifungal therapy included fluconazole (n=40), posaconazole (n=23), anidulafungin (n=1), and caspofungin (n=5). Median duration of cumulative days of voriconazole was 214 (range 2 -1553). SCC developed in 26/312 exposed to voriconazole and in 1/69 who received alternative antifungals. Cumulative incidence of SCC at 1 year was 3%, 2 years was 8%, 3 years was 13%, 4 years was 14%, and at 5 years was 19% (figure 1). Cumulative days of voriconazole use was found to be a risk factor for the development of SCC, and this relationship persisted in a multivariate model using previously identified risk factors (gender, age at transplant, TBI conditioning regimen, skin cancer pre-HSCT, chronic GVHD) as covariates (HR 1.859 for each 180 days of use, p<0.001). History of prior voriconazole exposure was not associated with an increased risk of SCC after covariate adjustment (HR 2.436, p=0.2369). Conclusion This is the first study to establish cumulative days of voriconazole use as a risk factor for SCC development following allo-HSCT, and may help guide appropriate antifungal prophylaxis in this patient population which is already at an increased risk of developing skin cancers. Disclosures: No relevant conflicts of interest to declare.

Abstract Introduction Although allogeneic hematopoietic cell transplantation (HCT) is an expensive modality of treatment for hematological disorders, very little is known about the financial burden for the patients themselves. We analyzed factors associated with financial burden and its impact on health behaviors of allogeneic HCT recipients. Patients and Methods A questionnaire was mailed to adult patients who were alive after allogeneic HCT performed between 1/06 to 6/12 at Mayo Clinic to collect information regarding financial concerns, household income, employment status, insurance, out-of-pocket expenses and health and functional status. A multivariable logistic regression analysis was performed to determine socio-demographic and clinical factors associated with financial hardship. Results Of 482 patients, 268 responded (response rate 56%). Respondents were more likely to be older and Non-Hispanic Whites. No significant differences were seen in disease or transplant characteristics between the two groups except that respondents were more likely to have received reduced intensity conditioning. Median follow-up after HCT was 2.3 years (range 0.7-6.7 years). All the patients for whom the insurance information was available (missing n=13) were insured. Median physical and mental component score, as derived from the SF-12, were 36.8 [Interquartile range (IQR) 29.3-49.0] and 53.1 (IQR 42.1-57.1) respectively, where the general population score is 50, and lower scores indicate worse functioning. The proportion of patients that reported being on medical disability increased from 8% prior to HCT to 29% after HCT. 73% of the respondents reported that being sick had hurt them financially. 54% experienced adverse financial consequences such as decrease in household income by &gt;50% due to the HCT, need to sell/mortgage home, withdraw money from retirement accounts or having to pay more for medical care than they could afford. 3% declared bankruptcy. 12% had out-of pocket costs for the past 3 months that were&gt; $5000. Median monthly medication copayments were $100 (range $ 0-3000). 36% patients felt that their insurance coverage was poor which was strongly correlated with adverse financial consequences (p=0.0013). Other risk factors for financial burden were poor physical functioning reflected by the physical component score &lt;40 (OR 3.2; p=0.005), lower household income (OR 3.08; p=0.006) and lack of commercial/private insurance (OR 4.2; p&lt;0.001) while adjusting for patient and transplant related characteristics. Time from transplant was a significant predictor (OR 1.2; p=0.03) in the univariate analysis, but lost its significance in the multivariate analysis. 18 to 27% patients reported deleterious health behaviors due to financial constraints such as not taking prescribed medications, not using a recommended medical service or not making physician appointments. Conclusions A significant proportion of allogeneic HCT survivors experience adverse financial consequences with a few reporting severe outcomes like bankruptcy, despite having health insurance coverage. Future research should investigate potential interventions such as early financial counseling and connecting with sources of financial support to help at-risk patients and prevent long-term adverse financial outcomes after this life-saving procedure. Disclosures: No relevant conflicts of interest to declare.

Abstract Background: Allogeneic hematopoietic stem cell transplantation (HSCT) is a potentially curative treatment for primary myelofibrosis (PMF). Reduced intensity conditioning (RIC) allows otherwise ineligible patients to proceed with HSCT. Host factors in PMF such as bone marrow (BM) fibrosis, massive splenomegaly, and transfusion related allo-immunization increase the risk of engraftment failure, especially with RIC. Spleen directed therapy (SDT) is often used in PMF patients with splenomegaly to help with engraftment, however little data exists supporting this practice. This study was carried out to investigate the role for SDT and the predictors of outcomes with RIC HSCT for PMF. Methods :After IRB approval, the Mayo Clinic HSCT registry was queried for patients with PMF that underwent RIC allo-HSCT from 2005-2014. Disease and transplant related data were retrospectively abstracted and analyzed for HSCT related outcomes. SDT was defined as a therapeutic strategy with specific intent to overcome an enlarged spleen prior to HSCT and included splenectomy, splenic artery embolization, splenic irradiation, or JAK inhibitor therapy that was stopped <30 days before HSCT. Survival estimates were calculated using the Kaplan-Meier method and means were compared using the log-rank test. Univariate and multivariate analyses were performed using Cox regression modeling. Results :51 patients (67% males) with WHO defined PMF with palpable splenomegaly that underwent RIC allo-HSCT were included in the study; median age 57 years (range, 35-68). The median follow-up was 12.2 months, and at last follow up, 19 deaths (37%) and 4 relapses (8%) were documented. The median OS for the group was not reached (mean 34.2 months); 88% at 100 days and 60% at 2 years. 17 deaths were attributed to non-relapse mortality (NRM). There were 3 engraftment failures (6%). 32 patients (63%) developed acute GVHD (grades II-IV) and 24 patients (47%) developed chronic GVHD (all grades). Twenty-one patients (41%) received SDT; 10 (48%) splenectomy, 2 (9%) splenic irradiation, and 9 (43%) JAK inhibitor therapy (ruxolitinib). The SDT group had a median spleen size of 14.5 cm (range, 1-29 cm) below the left costal margin (LCM) and 13 patients (62%) with spleen size >10 cm below LCM, while the no SDT group had a median spleen size of 7 cm (range, 1-19 cm) and 12 patients (40%) with spleen size >10 cm below LCM; p = 0.01. Seven (64%) of 11 patients receiving splenic irradiation (n = 1) or JAK inhibitor therapy (n = 6) were eligible for IWG-MRT spleen response, and 2 (29%) responded (both in JAK inhibitor group). Of the remaining 5 patients, 2 had a response not meeting IWG-MRT criteria. There were no differences in age (p = 0.09), gender (p = 1.0), DIPSS + score (p = 0.35), or HCT-CI (p = 0.61) between the two groups. There was a statistically significant difference in engraftment failure, with all 3 engraftment failures occurring in the SDT group (2 splenectomy patients, 1 splenic irradiation patient; p = 0.02). Engraftment failures were not attributable to insufficient cell dose, donor specific antibodies, or identifiable host factors. The patient with engraftment failure who underwent splenic irradiation had persistent massive splenomegaly. There were similar outcomes with regards to relapse rates, NRM, and acute and chronic GVHD. In the SDT group, the median OS was 13.3 months; 81% at 100 days and 33% at 2 years. In the no SDT group, the median OS was not reached; 94% at 100 days and 68% at 2 years; p=0.13. In a univariate survival analysis that included age, gender, SDT, DIPSS+ score, HCT-CI, CMV status, ABO status, HLA matching, donor source, graft source, engraftment status, and acute and chronic GVHD, predictors of survival were engraftment failure (p = 0.02) and major/bidirectional ABO incompatibility (p = 0.02). Similar results were obtained when JAK inhibitor therapy was considered separately from other forms of SDT. In a multivariate analysis, engraftment failure (HR 8.2, 1.8-27.2; p = 0.01) and major/bidirectional ABO incompatibility (HR 4.1, 1.4-10.9; p = 0.009) retained independent prognostic significance. Discussion:In patients with PMF and splenomegaly, there was no demonstrable benefit from SDT. Predictors of post-HSCT survival included engraftment failure and major/bidirectional ABO incompatibility. These findings need validation in a larger cohort of patients. Disclosures Al-Kali: Celgene: Research Funding. Mesa:Gilead: Research Funding; Incyte Corporation: Research Funding; Pfizer: Research Funding; Genentech: Research Funding; CTI Biopharma: Research Funding; Promedior: Research Funding; Novartis Pharmaceuticals Corporation: Consultancy; NS Pharma: Research Funding.

Abstract Background: Fludarabine plus busulfan (FB) and fludarabine plus melphalan (FM) are two commonly used reduced intensity conditioning (RIC) regimens for allogeneic hematopoietic stem cell transplantation (SCT). A recent analysis showed that both regimens had similar overall survival (OS) but relapse incidence (RI) was significantly higher with FB with a trend towards higher non-relapse mortality (NRM) in FM (Baron et al., Cancer 2015). However, that cohort included patients treated with oral and intravenous busulfan without pharmakokinetic targeting of intravenous which may impact anti-leukemic activity. Aim: Compare transplant related outcomes of FB vs. FM using intravenous (IV) busulfan targeted to the area under the curve (AUC). Methods: After due IRB approval, patients with acute myelogenous leukemia (AML) and myelodysplastic syndromes (MDS) receiving RIC-SCT from 2008-2014 were identified. All baseline and laboratory features were retrospectively extracted. Busulfan dose in FB was 0.8 mg/kg IV for 10 doses with therapeutic AUC target of 900-1500 mcmol/L (min). All patients received T-cell replete grafts. Categorical and continuous variables were compared using Pearson's chi-squared and Wilcoxon/Kruskal-Wallis, respectively. Survival estimates were calculated using the Kaplan-Meier method and curves were compared using the log-rank test. Cumulative incidence was computed as competing events using Grey's model. Univariate and multivariate analyses were performed using Cox regression modeling. Results: A. Baseline characteristics and AUC monitoring: 134 pts were identified (47 FB and 87 FM). Median follow up of the entire cohort was 40 months (0-63.3) and at last follow up, 60% and 29% have died or relapsed, respectively. Baseline characteristics stratified according to conditioning regimen are shown in table 1. Younger age (60 yrs FB vs. 61 yrs FM, p = 0.015) and a trend towards a higher CMV R-/D- status (28% FB vs. 14% FM p = 0.064) were the only significant differences identified. All patients in the FB group received intravenous busulfan and 46/47 patients had evaluable AUC data with a range of 732-1354 mcmol/L (min). A total of 19 patients were outside of range, all <900 mcmol/L (min) and required a median dose increase of 28.1% (3.3-50.2%) B. Engraftment and toxicity data: The median time for platelet engraftment was 19 days (0-48) for FB vs. 16 days (14-183) for FM (p = 0.0023) whereas the median time to absolute neutrophil count (ANC) engraftment was 18 days (7-30) for FB and 15 days (11-40) for FM (p = 0.077). Cumulative incidence of grade II-IV, III-IV acute GVHD and chronic GVHD at 2-yr was 57.3%, 11% and 52.8% for FB and 48.6%, 17% and 63.4% for FM (p = 0.73, 0.4 and 0.21, respectively). Two patients in the FM group died of cardiac causes (heart failure and sudden cardiac arrest). No cases of sinusoidal obstructive syndrome were observed in either arm C. Transplant outcomes: A significantly higher 2-yr relapse incidence (RI) was associated with FB vs. FM at 35.6% vs 17.3%, respectively (p = 0.0058). 2-yr progression free survival (PFS) was also significantly lower in the FB vs. FM at 51.2% vs. 65.1%, respectively (p 0.031). However, 2-yr OS and NRM was similar for FB vs. FM (53.1% and 22.9% vs 63.9% and 21.9%, respectively p = 0.26 and 0.89). Necessitating a dose adjustment based on AUC did not increase the risk for relapse or affect NRM. In multivariate analysis, FB was associated with increased RI with hazard ratio (HR) 2.29 (1.07-4.88; p = 0.033). Other factors significantly associated with RI on multivariate analysis were secondary/therapy related disease with HR 2.84 (1.34-6.02; p = 0.0067) and CR1 vs. other with HR 0.39 (0.17-5.32; p = 0.019). The significance of the results remained unchanged after exclusion of MDS patients (data not shown) Conclusion: Despite AUC dose adjustment, FB compared to FM was associated with increased RI with a similar OS and NRM. AUC dose adjustment did not impact transplant outcomes and its routine use in RIC should be further evaluated. Given the wide use of FB as a conditioning regimen, these important observations should be prospectively studied in a randomized fashion. Figure 1. Figure 1. Figure 2. Figure 2. Disclosures Al-Kali: Novartis: Research Funding. Wolf:Janssen Scientific Affairs, LLC: Consultancy.

Abstract Abstract 5226 Background Chronic myelomonocytic leukemia (CMML) is a clonal stem cell disorder with overlapping features between myelodysplastic syndromes and myeloproliferative neoplasms. Allogeneic stem-cell transplant (SCT) is considered to be a potentially curative option (Eur J Haematol. 2013; 90:355); with karyotype and comorbidity index (CI) being independent prognostic factors. The role of newer CMML prognostic models remains to be elucidated. We carried out this study to analyze the predictive value of the Mayo model (Leukemia 2013; 27:1504) in assessing transplant outcomes for patients with CMML. Methods After due IRB approval, 25 patients with WHO-defined CMML that underwent allo-SCT at Mayo Clinic from 1992 through 2013 were identified. All patients underwent bone marrow examination and cytogenetic evaluation at diagnosis. Clinical features including status at transplant, graft-versus-host disease (GVHD) prophylaxis, donor-recipient HLA-matching, donor-recipient blood types and CMV status were documented. Patients were evaluated for development of GVHD, disease relapse, remission status, and death from all causes. We evaluated the prognostic relevance of clinical and laboratory parameters including those previously identified by the MDAPS (Blood 2002;99:840), Spanish cytogenetic stratification (Haematologica 2011;96:375), and the recently described Mayo model Results Among 25 study patients, 14 (56%) were males and 15 (60%) had WHO defined CMML-1 (6-symptomatic/transfusion dependent, 3-monosomy 7). The median age at transplant was 51 years (range, 18-66 years). Graft sources included: 19 (76%) peripheral blood, 5 (20%) bone marrow, and 1 (4%) double umbilical cord blood. Ten (40%) patients received a reduced intensity conditioning. At last follow up, 15 (60%) deaths were documented while the remainders are alive and disease free. There were six (25%) post-transplant relapses all resulting in mortality. The 5-year OS was 42% and the 5-year non relapse mortality was 35%. Based on the Mayo model, 15 (60%) patients received a high-risk prognostication, 6 (24%) were intermediate and 3 (12%) were low. In an univariate analysis that included: demographics, blood counts at diagnosis and transplant, WHO classification (p=0.19), Spanish karyotypic stratification (p=0.67), prognostication according to the MDAPS (p=0.35) and Mayo model, disease status at transplant, SCT comorbidity index (p=0.06), graft sources, transplant conditioning regimens (p=0.08), development of acute (p=0.64) and chronic GVHD (p=0.06); thrombocytopenia at diagnosis (p=0.04), disease status at transplant (p=0.02), and a high risk prognostication using the Mayo model (p=0.01) were statistically significant. On a multivariable analysis only high risk prognostication by the Mayo model (p=0.02) retained its negative prognostic impact. In an univariate analysis for relapse-free survival, risk stratification by the Spanish cytogenetic system (p=0.04) and the Mayo model were prognostic (p=0.01), with the high risk prognostication by the Mayo model retaining its negative prognostic impact (p=0.01). Conclusions Allogeneic SCT remains a viable treatment option for patients with CMML. The Mayo model serves as a valuable tool, helping with the identification of high risk CMML patients. These patients seem to benefit from allo-SCT in comparison to non-transplant therapeutic options. Given the smaller sample size, validation in a larger patient cohort is needed. Disclosures: No relevant conflicts of interest to declare.