HLA-identical Donor Research Articles

Inferior Overall Survival After Haploidentical Donor Lymphocyte Infusions in Relapsed Myeloid Neoplasms.

Allogeneic hematopoietic stem cell transplantation (HSCT) effectively treats high-risk myeloid neoplasms, but relapses post-HSCT, particularly in acute myeloid leukemia (AML) and myelodysplastic neoplasms (MDS), pose significant challenges. Donor lymphocyte infusion (DLI) has been utilized, but its effectiveness, especially in haploidentical settings, remains insufficiently clarified, and graft-versus-host disease (GvHD) poses a substantial risk. In this retrospective cohort study, 57 patients with AML or MDS who received DLI after allogeneic HSCT at our center from 2002 to 2023 were analyzed. Herein, only preemptively or therapeutically applied DLI were included, and endpoints included overall survival (OS), progression-free survival (PFS), and GvHD incidence post-DLI. Median OS after DLI was 517 days, with a 1-year OS of 62.5%. Factors associated with longer OS included patient age, HLA-identical donor, post-HSCT treatment naivety, and preemptive DLI indication. Haploidentical DLI was associated with inferior OS compared to HLA-identical DLI; however, PFS and GvHD incidence post-DLI did not differ significantly. Our study findings indicate that OS rate is inferior in patients with relapsed AML or MDS treated with haploidentical DLI in comparison to those who received HLA-identical DLI. Given the limitations of haploidentical DLI, alternative strategies, such as higher cell doses or combination treatment approaches, warrant further investigation.

Improved Outcomes in Myelofibrosis after Allogeneic Stem-Cell Transplantation in the Era of Ruxolitinib Pretreatment and Intensified Conditioning Regimen—Single-Center Analysis

(1) Background: Allogeneic hematopoietic stem-cell transplantation (allo-HSCT) is the only treatment with the potential for cure in patients with myelofibrosis (MF). However, the risk of graft rejection, which is particularly high in MF, and the risk of significant non-relapse mortality must be considered. (2) Methods: In this retrospective, single-center study, we compared allo-HSCT outcomes in 36 adult patients with MF transplanted at two-time intervals (2001–2015 versus 2016–2021). (3) Results: The estimated median overall survival was 48.9 months (95%CI 0.00–98.2) in the cohort transplanted before 2016 and not reached in the more recent years (p = 0.04) due to markedly lower non-relapse mortality (p = 0.02). The 3-year relapse incidence was low in both cohorts (11.1% and 12.5%, p > 0.99). When comparing only subgroups within the more recent cohort based on the presence or absence of total body irradiation (TBI) or the use of sequential regimens, OS and PFS were comparable. (4) Conclusion: Pretreatment with ruxolitinib, intensified conditioning, and the preferential use of haploidentical related instead of mismatched unrelated donors for patients lacking an HLA-identical donor are most likely responsible for the improved outcome after allo-HCT in MF in recent years.

Feasibility of co-transplantation of umbilical cord blood and third-party mesenchymal stromal cells after (non)myeloablative conditioning in patients with hematological malignancies

Umbilical cord blood (UCB) is an alternative source of stem cells for patients lacking a 9/10 or 10/10 HLA identical donor. However, after UCB transplantation, time to engraftment and immune recovery are prolonged, increasing the risk of fatal complications. Mesenchymal stromal cells (MSC) can support hematopoietic engraftment and have immunosuppressive effects.The primary objective of this phase I/II multicenter study was to determine the feasibility and safety of UCB transplantation with co-infusion of third party MSC, as assessed by treatment related mortality (TRM) at day 100. Secondary objectives were engraftment, immune recovery, occurrence of graft versus host disease (GVHD), infections, disease free survival, relapse incidence and overall survival.Eleven patients were grafted according to this protocol. Allogeneic transplantation after co-infusion appears feasible with 18 % TRM at day 100. Engraftment data show a median time of 16 days to neutrophil and 27 days to platelet recovery, which is shorter than what is usually reported after UCB transplantation. Only 1 episode of acute GVHD was reported.In conclusion, MSC and UCB co-transplantation is feasible and might help overcome some of the drawbacks of UCB transplantation.

Hematopoietic cell transplantation for older acute myeloid leukemia patients in first complete remission: results of a randomized phase III study.

Given the selection of elderly patients with AML in first complete remission (CR1) the advantage of consolidation with allogeneic hematopoietic cell transplantation (HCT) over chemotherapy is still unclear. Newly diagnosed AML patients in CR1 aged 60-75 years were registered and a donor search initiated. After one consolidation cycle, patients with a matched donor were randomized to HCT with fludarabine/lowdose total body irradiation and cyclosporine/mycophenolate mofetil immunosuppression or conventional non-HCT. Primary outcome was restricted mean leukemia-free survival (RM-LFS) up to five years. Between 2010 and 2017, 245 patients (median age 67 years) were registered at CR1. After one consolidation, 26.9% of patients failed inclusion criteria. Of the 179 (73%) patients still on study, 75.4% had an HLA identical donor. Ten ineligible patients were excluded, and 125 randomized to HCT (n=83) or non-HCT (n=42). The primary outcome RM-LFS up to 5 years was 24.5 months (95%CI:18.9-30.1) in the HCT and 15.6 months (95%CI:10.4-20.8) in the non-HCT arm (p=0.022) due to a decrease in cumulative relapse incidence from 91.1 (95%CI:80.7-100.0) after non-HCT to 37.8 (95%CI:27.2-48.4)% after HCT (p.

Comparison of Cyclophosphamide-Based Graft Versus Host Disease Prophylaxis after "Allogeneic Stem Cell Transplantation from 9/10 HLA Matched Unrelated Donor'' with Standard Graft Versus Host Disease Prophylaxis after "10/10 HLA Matched Relative Donor'' Transplant.

Background: Graft Versus Host Disease (GvHD), which can be observed at a rate of 30-80% after allogeneicstem cell transplantation (ASCT) is an important complication that adversely affects the survival and quality of the life of patients.Posttransplant cyclophosphamide (PTCy) effectively prevents GvHD after HLA-haploidentical ASCT. In our study, the use of PTCy in 1-antigen HLA-mismatched unrelated donor (9/10MMUD) ASCT was compared with standard GvHD prophylaxis in HLA-identical related donor (MRD) ASCT. Materials and Methods: We conducted a retrospective study of the comparison of 42 patients with 9/10 MMUD ASCT receiving PTCy+Methotrexate (MTX)+Calcineurin Inhibitor (CNI) and 37 patients with HLA-identical MRD who received MTX+CNI in 3 bone marrow transplantation centers. Results: Cumulative incidences of grade I-II (64.6% vs 45.4%, p=0.187) or grade III to IV acute GvHD (35.4% vs54.6%,p=0.187)and chronic GvHD (11.9% vs 29.7%, p=0.096) were similar in the PTCy group and control group. No statistically significant differences were observed between PTCy and the control group in overall survival rate (52.4% vs 62.2%, p=0.381), progression-free survival (1483.97 vs 1200.70 days, p=0.502), relapsed-related mortality rate (21.4% vs 16.2%, p=0.556) and treatment-related mortality rate (16.7% vs 21.6%, p=0.575). Conclusion: With the addition of PTCy to standard GvHD prophylaxis in 9/10MMUD ASCT, the risk of GvHD due to incompatibility and unrelated transplantation is eliminated, and transplantation success is achieved with MRD ASCT. PTCy-based prophylaxis is an effective and safe strategy to prevent GvHD in 9/10 MMUD ASCT without increasing the risk of relapse and treatment-related mortality.

Probability of finding an HLA-identical donor for hematopoietic stem cell transplantation in immediate families: The Tunisian experience

Probability of finding an HLA-identical donor for hematopoietic stem cell transplantation in immediate families: The Tunisian experience

Comparison of Outcomes of Hematopoietic Cell Transplantation (HCT) for Asymptomatic Patients with Sickle Cell Disease (SCD) and That of Propensity Matched Symptomatic Patients Undergoing HCT

Introduction Hematopoietic cell transplantation (HCT), a potential curative option for sickle cell disease (SCD) has typically been offered to patients with severe disease manifestations. With improved outcomes, especially in young children receiving HCT from HLA identical donors, some clinicians are performing HCT for patients without severe manifestations. HCT is associated with risk of substantial short-term morbidity, death, and long-term sequelae. Performance of HCT in patients who have not yet suffered from complications of SCD, raises unique issues of cost-benefit tradeoff, ethics, and healthcare equity. Further, it is unknown whether patients who have not suffered complications of SCD would have better outcomes following HCT. The objective of this study was to compare the outcomes for asymptomatic patients in patients undergoing HCT for SCD and propensity matched symptomatic SCD patients undergoing HCT. Methods: We queried the HCT for SCD dataset of patients undergoing HCT between 1990-2022 and reported to the Center for International Bone Marrow Research (CIBMTR) registry. Transplant essential data had been submitted for all patients while a subset of patients was assigned to the comprehensive research form (CRF) track. On these patients HCT centers submitted detailed SCD specific baseline data, as well as outcomes relevant to SCD and organ specific complications. The main reason for HCT is one of the variables collected in the CRF. Thus, we selected patients in the CRF track for further study. We describe demographics, baseline characteristics, transplant essential outcomes including overall survival (OS) and event free survival (EFS), graft failure (GF), Acute graft versus host disease (aGVHD) and chronic GVHD (cGVHD), venocclusive disease of the liver (VOD), post-transplant pneumonia/acute chest syndrome or other pulmonary complications(ACS), nephropathy, stroke, avascular necrosis (AVN), vasocclusive crises (VOC). We created a propensity score model, adding baseline variables. For each categorical outcome variable, frequency tables and tests of difference in proportions were derived. Descriptive statistics and tests of difference in means were derived for the two numeric outcome variables. In addition, survival analysis (Cox regression modeling) was conducted to determine the time until an individual experienced graft failure or death and whether event rates were associated with group classification adjusting for age and donor type. Results: For the entire cohort of 1718 patients undergoing HCT from 1990 to 2022 patients were followed for a median 47.8 months (0.3-312.9), 73.4% of patients with age at HCT <18 years and 74.7% with Karnofsky-Lansky score ≥ 90. The 3-year OS was 91.2%, 3-year EFS 75.5%, and GF rate was 17.9%, aGVHD grades II-IV occurred in 18.3%, and cGVHD developed in 22.3%. A total of 763 patients were assigned to the CRF track. The main reason for HCT was reported for these patients, and 49 patients were reported to be asymptomatic at baseline. In the asymptomatic patients majority of the HCT were performed for patients under the age of 10 years (n = 33) in patients with Hemoglobin SS (n = 45) and most occurred between 2013-2018 (n = 24). Average follow up period was 48 months. The most common graft source and conditioning regimens utilized were bone marrow (n = 35) HLA identical sibling donor type (63.2%, n = 31), and reduced intensity conditioning (n = 25) respectively. Other donor types included HLA mismatched relative (n = 9), mismatched unrelated donor and cord blood (n = 5), and matched unrelated was used in 4 patients. There was one death, at 16.5 months with cGvHD. GF occurred in 14.3%, OS was 97.9%, EFS 83.67%, 20.4% developed aGvHD and 28.5% developed cGvHD and none developed secondary malignancies or post-transplant lymphoproliferative disorders. Propensity matched control group (Figure 1) was constructed based on age at HCT, donor type, graft type, HCT comorbidity index, SCD type. There was good variable balance with a small standardized mean difference for matched observations. There were no statistically significant differences in least mean squares for EFS, death, OS, GF, AGVHD, CGVHD, VOD, VOC, AVN, stroke or ACS between the propensity matched groups ( Figure 1). Discussion: Complications and outcomes of HCT in asymptomatic patients with SCD patients is similar to that in propensity matched symptomatic SCD patients undergoing HCT.

Similar Overall Survival and Event-Free Survival for Patients Under or over the Age of 14 Years, but More Chronic Graft Versus Host Disease and Non-Relapse Mortality in the “Older” Patients

Purpose: In the prospective, randomized, multinational FORUM trial, total body irradiation and etoposide were statistically more effective than chemoconditioning (Peters et al, JCO 2021; FORUM study; EudraCT: 2012-003032-22; ClinicalTrials.gov: NCT01949129). The multivariate analysis in this cohort showed an inferior overall survival (OS) for patients (pts) over the age of 10 years, HR 1.8 (95% CI, p=0.048). To update these findings, we examine the impact of age at allogeneic hematopoietic stem cell transplantation (HSCT), we analyzed 791 FORUM pts who received TBI and etoposide as conditioning regimen between April 2012 and March 2022 and compared their outcomes according to different age categories. Patients and Methods: Almost all patients were transplanted in second or first complete remission (CR2) (47%, n=370; CR1: 46%, n=361, >CR3: 8%, n=59), from matched unrelated donors (MUD) 70%, n=552, HLA-identical sibling donors (MSD) 30%, n=239, bone marrow (BM) 70%, n=551, or cord blood (CB) 3%, n=26. Median age at HSCT was 10 years (4-21). Median observation time was 2.3 years (0.3 to 8) (Table 1: Basic Characteristics). The conditioning regimen consisted of total body irradiation (TBI) - 6 fractions of 2 Gy on 3 consecutive days followed by 60 mg/kg body weight etoposide (max 1800 mg/m2, total upper dose limit 3.6 g). GVHD prophylaxis was CSA only for MSD receiving bone marrow. ATG/CSA/MTX was used for the MUD HSCT group. Results: 127 evaluable pts were transplanted between 4-6 years (group 1), 249 between 6-10 years (group 2), 231 between 10-14 years (group 3), and > 14 years were 184 pts (group 4) (n.s.) By the 4 age groups, the 5-year OS was 0.83±0.04 (group 1), 0.75±0.04 (group 2), 0.75±0.04 (group 3), and 0.74±0.04 (group 4), respectively, p = 0.133. Five-year event-free survival (EFS) was also similar for all age groups: 0.71 ± 0.06, 0.72 ± 0.04, 0.66 ± 0.05, 0.69 ± 0.04 (p=0.611): Figure 1. The three-year cumulative relapse incidences (CIR) were 0.23±0.04, 0.19±0.03, 0.14±0.03, and 0.17±0.03, respectively (p=0.286). Non-relapse mortality (NRM) was significantly lower in the two younger age groups (0.02 ± 0.01 group 1 and 0.05 ± 0.02 group 2) compared to 0.11 ± 0.02 in both older age groups (p = 0.047). The primary causes of death in the 18/184 pts in group 4 were as follows: infections (fungal, viral, bacterial): n=8, acute and chronic graft versus host disease (aGVHD, cGVHD): n=3, sinusoidal obstruction syndrome, coagulopathies: n=4, multi-organ failure: n=3. Among the 767 evaluable pts, 503 (66%) had no or grade1 aGVHD, 188 (25%) had grade 2 aGVHD, and 76 pts (11%) had grade3 to 4 aGVHD; in patients > 14 years 22 (14%) had a grade 3 to 4 aGVHD (p = 0.624). The 3-year incidence of extensive cGVHD was significantly higher in pts older than 14 years (0.21±0.03 vs. 0.10±0.03, 0.11±0.02 and 0.14±0.03, respectively), which also translated into significantly better extensive cGVHD-free, relapse-free survival (cGRFS) for the younger cohorts (Table 1). To date, the overall incidence of secondary malignancies in this cohort is 0.01 (n = 11) with no significant differences in the 4 age categories. In the age group > 14 years, in 98 pts transplanted in first CR vs. > CR1 (n=86), 5-year OS is 0.83±0.04 and 0.63±0.06, respectively (p=0.005). Similarly, 5-year EFS was 0.79±0.05 and 0.56±0.07, respectively (p=0.002). In multivariate analysis, OS, EFS, CIR was not influenced by donor type and pts' age at transplant. However, NRM was higher in pts older than 14 years, the hazard ratio (HR) being 4.8 (1.4-16; p=0.012) as compared to patients aged 4-6 years. Remission status (CR1 vs. >CR1) had significant impact on EFS with HR of 1.6 (1.1-2.1; p= 0.004) and CIR (HR 1.7; 1.1-2.4; p= 0.012). Conclusions: In the FORUM trial, patients who underwent allogeneic HSCT from HLA-identical or HLA-matched unrelated donors older than 4 years and younger than 21 years who received myeloablative conditioning with TBI/etoposide had similar overall and event-free survival regardless of age at HSCT. The incidence of chronic GVHD and NRM was higher in patients > 14 years compared to younger patients.

Casting Hope, Defying Odds: Unveiling the Impact of Haplo-Identical Stem Cell Transplant in Myeloid Malignancies - a Tertiary Cancer Care Center Experience

Background & Significance: Only 30% to 40% of patients in need of a curative stem cell transplant (SCT) could find a suitable matched sibling donor. For Indian patients, the likelihood of locating a 10/10 HLA identical unrelated donor within limited donor registries is approximately 14%. However, this probability has the potential to rise to 60% if registries with over 1,000,000 registered donors are available. 1,2 Consequently, there is an increasing inclination in India to perform haploidentical transplantations utilizing the post-transplantation cyclophosphamide (PTCY) platform developed by the Johns Hopkins group. 3 The outcomes of haploidentical stem cell transplantation (haplo-SCT) for the treatment of AML were enhanced in the 1990s with the introduction of a T-cell depletion (TCD) strategy followed by a myeloablative conditioning regimen. 4,5 In the last two decades, significant progress in haplo-SCT for hematological malignancies, especially AML, includes donor selection algorithms, improved grafts, GVHD prophylaxis, and enhanced immunologic recovery, benefiting patients. 6 Here, we present our experience of haplo-identical stem cell transplants in myeloid malignancies at our centre. Study design & Methods: We conducted a retrospective study at our site. Patients with myeloid malignancy who underwent haplo-identical stem cell transplant between Jan 2018 - Jan 2023 were included in the study and the follow-up was done till July 2023. Haplo-identical transplants done for diagnosis other than myeloid malignancy were excluded. The objectives of the study were to assess the non-relapse mortality [NRM] rate at day +100, relapse rate, graft-versus-host disease - free relapse-free survival [GRFS] and overall survival [OS] of the study cohort. GRFS was defined as a combined outcome including mortality from any cause, recurrence of malignancy, acute GVHD of grade 3 to 4, or chronic GVHD necessitating systemic immune suppression therapy. 7 Descriptive statistics (including median, mean, and range) were used to describe the central tendency and dispersion of variables. The probability of overall survival [OS] and graft versus host disease relapse free survival [GRFS] was estimated by the method of Kaplan and Meier. Probabilities of relapse or progression of malignancy, RRM, and day-100 NRM were summarized using cumulative incidence estimates All statistical analysis were done using statistical package for social science software (SPSS 21, IBM SPSS Statistics). Results: We have analysed 29 patients with various myeloid malignancies who have underwent haploidentical SCT from Jan 2018 to Jan 2023. There were 28 AML and 1 MDS patients. The median age was 35 (range, 16 - 59) and there were 22 males and 7 females. Conditioning intensity was myeloablative in 19 (65.5%), reduced intensity conditioning (RIC) in 8 (27.6%) and NMA in 2 (6.9%) patients. There were 10 (34.5%) patients in complete remission 1(CR1) and 19 (65.5%) in CR2. Hematopoietic Cell Transplantation-specific Comorbidity Index [HCT-CI] score was as low 11 (37.9%), intermediate 8 (27.6%) and high 10 (34.5%) patients respectively. Median time to neutrophil engraftment was 16 days (range, 12 - 25) and platelet engraftment was 17 days (range, 11 - 32). Median CD34 stem cell dose was 6.25 x 10*6/kg (range, 3.1 - 8.09) x 10*6/kg. Grade II-IV acute GVHD over first +100 days post SCT was observed in 6 (20.7) patients, and grade III-IV acute GVHD and chronic GVHD at follow up of one year was 3 (10.3) respectively. CMV reactivation by +100days was seen in 18 (62.06%) patients. Relapse was seen in 10 (34.5%) patients, out of which 2 patients are alive and 8 expired due to progressive disease. At median follow up of 13 months, OS is 60.3% (CI: 39.7% - 75.9%) and GRFS is at a median follow-up of 6 month was 51.2% (CI: 35.6% - 71%). Fig:1 NRM was 10.3% and 17.24% at +100 days and at last follow-up respectively. Fig:2 Conclusion: In conclusion, our study demonstrates favorable outcomes in terms of NRM (non-relapse mortality) with a low rate of 10.3% at 100 days after haploidentical SCT. The results also show promising overall survival (OS) and GVHD-free, relapse-free survival (GRFS) rates, supporting the potential of haploidentical transplants as an effective treatment option for myeloid malignancies. Further long-term follow-up and research are needed to validate and optimize these findings.

Allogeneic Bone Marrow Transplantation from HLA-Identical or Haploidentical Donors for Children and Adolescents with Sickle Cell Disease: A Feasible Curative Option

The only curative option widely available for sickle cell disease (SCD) is bone marrow transplantation (BMT). Since few patients have a healthy matched sibling donor (MSD), haploidentical (haplo) donors have expanded the donor pool to approximately 90% of the patients. The addition of thiotepa to the Johns Hopkins conditioning therapy backbone dor haplo BMT showed durable engraftment and excellent overall survival. However, graft rejection has remained an important obstacle. Our challenge in these patients has been to augment the conditioning therapy to provide adequate engraftment, while maintaining a low transplant-related mortality. Methods: Retrospective data of all 26 patients with SCD followed by our group after MSD (n=7) and haplo (n=19) BMT performed in four different institutions. With a MSD, conditioning was rATG 4.5mg/kg, Busulfan (Bu, AUC 4,500), Fludarabine (Flu, 120mg/m²) or rATG, Bu, Cyclophosphamide (Cy, 200mg/kg) and with haplo donors, rATG 4.5mg/kg, Thiotepa 10mg/kg, Flu 150mg/m², Cy 29 mg/kg and TBI 2Gy. Patients were prepared to BMT with intense hypertransfusion/bleeding or erythrocytapheresis to keep HbS<30 and Hb~10g/dL, reticulocytes <10% for 2-3 months prior to BMT, with intensive chelation to keep ferritin <1,000ng/mL. The presence of donor specific antibodies would exclude the patient from undergoing BMT. Due to two consecutive secondary graft failures (no detectable donor cells despite initial engraftment) and two falling mixed chimerism among the first 13 patients undergoing haplo, the doses of the conditioning therapy were increased to Cy 50 mg/kg and TBI 4Gy in a single fraction, as previously used in our patients with aplastic anemia undergoing BMT. Six consecutive patients received this augmented conditioning therapy. All patients had serial chimerism measured by STR. The graft-versus-host disease (GVHD) prophylaxis included Cyclosporine - Methotrexate in MSD and post-transplant Cy/mesna, mycophenolate mofetil and sirolimus in haplo. Results: Between September 2016 and April 2023, 26 patients underwent BMT, with a median age of 11 years (4-20), half of them females, 7 with a MSD and 19 an haplo (4 siblings, 6 fathers, and 9 mothers); 77% of the donors had sickle cell trait. The graft was bone marrow in all but one patient with Sb thal and Hodgkin's lymphoma. The median follow-up was 15.5 months. All patients engrafted. BMT with MSD had excellent outcomes and stable chimerism. Among the first 13 patients undergoing haplo, secondary graft failure occurred very suddenly in two patients (CD34 cell doses of 2 and 8x10 6 CD34/kg), both male teenagers; two additional patients had a significant drop in chimerism up to 30% donor cells but responded to serial donor leukocyte infusions 1-5 x10 6 CD3/kg (2 and 6) and developed very mild skin GVHD. The other patients maintained > 89-100% donor cells. Thereafter, with the augmented conditioning regimen, all six consecutive patients have stable 100% donor chimerism. Acute II-III GVHD was observed in 34% and chronic GVHD in 15% of the patients. Viral reactivations (CMV, HHV6, BKV, HHV7 and EBV) were observed in all patients. Overall survival is 100% and rejection-free survival is 83% at 1 year (Figures 1, 2). Conclusions: Allogeneic BMT with an HLA-identical or haploidentical family donor was feasible to treat SCD with an excellent overall survival. With a larger cohort and longer follow-up, the long-term effects of this strategy will be thoroughly studied.

TCRαβ +/CD19 + - Depleted HLA-Haploidentical Hematopoietic Stem Cell Traansplantation in Pediatric Patient with Fanconi Anemia

Background Allogeneic hematopoietic stem cell transplantation (HSCT) currently represents the only proven treatment able to rescue bone marrow failure and prevent the occurrence of clonal evolution in patients with Fanconi Anemia (FA). If HSCT from HLA-identical related donor (MRD) is reported to be associated with better outcomes, this is not available for most patients. On the other hand, the identification of a fully matched unrelated donor (MUD) may be unsuccessful, or require times incompatible with a prompt treatment of the haematological condition. For patients who lack a MRD or MUD, the preferred donor choice is debated. HLA partially matched haploidentical donor (haplo) is virtually immediately available for all patients and haplo-HSCT has been reported over the last few years as a promising alternative for those patients. Following the favorable results already reported from our group of a cohort of pediatric and young adult FA patients underwent haplo-HSCT, based on the selective depletion of TCRαβ + and CD19 + cells graft manipulation, here we present the outcome of an enlarged cohort of patients who received HSCT in 3 different centers. Methods Patients diagnosed with FA and eligible for an allogeneic transplantation, but lacking a MRD or MUD, and with a suitable HLA-haploidentical donor were eligible to this study. The conditioning regimen included intravenous fludarabine, cyclophosphamide and single-dose total body irradiation for most patients. Pretransplant anti-T-lymphocyte globulin was administered in all patient to control in vivo bidirectional donor-recipient alloreactivity. Apheresis and graft manipulation were performed as previously reported (Li Pira, Biol Blood Marrow Transplant 2016). Results Thirty-five patients (19 males and 16 females) underwent haplo-HSCT between September 2011 and April 2023 in 3 different centers (Bambino Gesù Children's Hospital, Rome, Italy; Policlinico San Matteo, Pavia, Italy; Tokyo; National Center for Child Health and Development, Children's Cancer Center, Tokyo, Japan). Twenty-four patients have been previously reported (Strocchio, Blood Adv 2021). Details on patients and donor characteristics, graft composition and conditioning regimen are listed in table 1. One patient with clonal evolution and 1 with AML received fludarabine and AraC 3 weeks before the start of the conditioning. Primary engraftment was achieved in 33 patients (94.3%), with median time for neutrophil and platelet recovery of 12 days (range, 9-20 days) and 10 days (range, 7-14 days), respectively. Primary graft failure occurred in 2 patients and both were successfully transplanted from the other haploidentical parent. The monitoring of chimerism analysis confirmed a stable engraftment of donor hemopoiesis in all engrafted patients. Within 33 evaluable patients, 9 (27.3%) experienced grade 1-2 aGvHD (7 with stage I-II skin-only involvement, 1 with stage I lower gastrointestinal involvement) at a median time of 35.5 days (range, 16-67 days) after HSCT. One patient developed late-onset skin only grade 2 aGvHD at day +211 after HSCT. One patient (3%) experienced grade IV aGvHD (liver and gastrointestinal involvement) at day + 100 from HSCT, 4 weeks after the infusion of adenoviral-specific donor T cells; he is currently receiving ruxolitinib and the complete resolution of GvHD was obtained. Only one patient (3%), developed cGvHD with mild skin involvement. Thirteen patients (39.4%) experienced one or more viral infections or reactivations (6 cytomegalovirus, 4 herpesvirus-6, 2 adenovirus, 1 parainfluenzae); the specific antiviral treatment was administered with a complete resolution of infection in all cases. With a median follow up of 5.5 years (range, 0.6-11.4 years) all the patients are alive and with resolution of hematological complications. Except for the already reported vulvar intraepithelial neoplasia, no additional posttransplant malignancy was observed Conclusions Our data obtained from enlarged cohort of patients previously reported, confirm excellent results in terms of survival and a good rate of engraftment also in a multicenter setting. The low incidence of acute and chronic GvHD, a particularly detrimental complication in patients with DNA repair disorder, makes this approach attractive in this patient population. In FA patients lacking a standard donor, TCRab +/CD19 + haplo-HSCT is confirmed to be a promising strategy.

Moderate Incidence but Striking Correlation with TBI of Secondary Malignancies after HSCT in Children with ALL: Long-Term Follow-up from the Prospective International BFM- and Forum-Trials

Introduction: Total body irradiation (TBI)-based conditioning was found to be associated with superior leukemia-free survival when compared to chemo-based conditioning for children with ALL undergoing allogeneic hematopoietic stem cell transplantation (HSCT) in the prospective, international, randomized FORUM trial (Peters et al, JCO 2021). Nevertheless, TBI is considered as the major risk factor for developing secondary malignancies (SM). We and others have previously reported the incidence, risk factors, and outcomes of SM after HSCT in children with ALL (Eichinger et al, Leukemia 2022), but prospective studies of SM after HSCT in children are limited. Therefore, we analyzed the results of 2151 patients enrolled in the prospective BFM 2003 and the FORUM trial from 2003-2022. Patients and methods: We included data from all 668 patients (pts) treated in the BFM 2003 trial and from all 1483 patients treated in the FORUM trial with HSCT from HLA-identical family donors (MFD, 26% of patients), matched unrelated donors (MUD, 65%), and either related or unrelated mismatched donors (MMD, 9%). In the BFM 2003 trial pts >2 years (y) of age years were offered TBI/VP-16 (12 Gy TBI in 6 fractions of 2 Gy each, given as 2 fractions per day for 3 days; VP-16 60 mg/kg, maximum total dose 3600 mg) as conditioning. Only pts with contraindications for TBI received chemo-conditioning, which consisted of i.v. busulfan, cyclophosphamide and etoposide. In the FORUM trial pts >4y of age were randomized to receive either TBI- or chemo-based conditioning regimens; pts <4y were allocated to the chemo-conditioning arm consisting of fludarabine/thiotepa and either busulfan or treosulfan. Details on the transplant procedure have been previously described (C. Peters, et al. JCO 2015 /2021). Results: Centres from 31 countries on 5 continents contributed to the two studies. The median age was 9.2 (range 0.5-23) y. The majority were male (63%, 1356/2151) and >2 y of age at HSCT (94%, n=2024). TBI-based conditioning was applied in 64% (n=1429), while 34% (n=722) of pts received chemo-conditioning. TBI/VP16 was given in 27% (43/159) of age group 2-4y, and in 76% (1269/1672) of age group >4y. With a median follow-up of 3.29 (range 0.1-16.4) y, a total of 46 SM (33 in BFM 2003, 13 in FORUM) were diagnosed at a median of 5.12 (range 0.4-13.4) y post HSCT, all but one in the TBI group. Four pts experienced ALL relapse prior to the occurrence of the SM leaving 42/2151 cases for further analysis. The 5-, 8-, and 10-y cumulative incidence (CI) of SM, with relapse and non-relapse mortality being competing events, were 0.02 (±0.01), 0.06 (±0.01), and 0.13 (±0.03), respectively. Details of the SM are described in Table 1. Regarding age at HSCT, no SM was observed in the very young age group (<2 years) (0/127), 4 SM in the 2-4 years group (2.2%, 4/181), 20 SM in the 4-10 years group (2.3%, 20/867), and 22 SM in the >10 years group (2.25%, 22/976) (p=n.s.). Six patients developed an additional SM: these were MDS (n=2), and glioblastoma, breast cancer, basal cell carcinoma, and squamous cell carcinoma (one each). The first SM occurred at a median of 5.12 (range 0.4-13.4) y, and the additional SM at 10.7 (range 4.3-12.1) y after HSCT. The probability of OS after SM diagnosis was 0.65 (±0.008) at 5y and 0.32 (±0.17) at 10y. Causes of death were SM in 12/14 cases and 2/14 ALL relapse-associated. All 3 glioblastoma-pts died within 8 months after diagnosis. 17/18 pts (94%) with thyroid cancer were alive at last follow-up (0-10 y after SM diagnosis). As shown in Figure 1, the 8-y CI of SM differed significantly between TBI- and chemo-conditioning (0.08[±0.02] versus 0.04[±0.04], p=0.004) in both age groups (2-4 y and >4 y). No significant correlation was observed with patient characteristics such as age, gender and ALL remission status. In addition, we did not identify other statistically significant transplant-specific risk factors including donor type, stem cell source, grade II-IV and III-IV aGVHD and cGVHD. Conclusions Updated data from two prospective studies using uniform regimens confirmed TBI-based conditioning as a risk factor for SM in pediatric ALL. Further analysis is ongoing regarding the association with immune phenotype of ALL and details of genetic risk factors (e.g. TP53 mutations). Rigorous long-term FU of TBI patients is mandatory.

Phase I/II Study of Reduced Dosing of Post-Transplantation Cyclophosphamide (PTCy) after HLA-Identical Peripheral Blood Hematopoietic Stem Cell Transplantation

Introduction Post-transplant cyclophosphamide (PTCy)-based prophylaxis for acute graft versus host disease (aGvHD) has become a standard protocol in HLA haploidentical bone marrow transplantation. Preliminary evidence indicates that compared to the standard dosage (50 mg/kg on days +3 and +4 post-transplantation), a regimen of half the typical cyclophosphamide dosage is both feasible and effective. However, the optimal dosage and timing of PTCy for aGvHD prophylaxis in a HLA identical setting, using peripheral stem cells as the graft, remain unknown. This study aims to investigate the efficacy and safety of a reduced PTCy dosage regimen in patients undergoing peripheral blood stem cell transplants (PBSCT) with HLA indentical donors. Methods This prospective, single-center phase I/II study enrolled patients scheduled for PBSCT with HLA identical donors. The aGVHD prophylaxis regimen comprised PTCy on days +3 and +4, followed by cyclosporine initiation from day 5 post-transplant. In the phase I stage, an initial cohort of five patients received PTCy at a dosage of 50 mg/kg/day on days +3 and +4 (designated as dose level 1, DL1). This was followed by a 3+3 dose de-escalation design with subsequent dose levels as follows: DL2, 50 mg/kg on day +3 and 25 mg/kg on day +4; and DL3, 25 mg/kg on both day +3 and +4. The dose-limiting toxicity for this de-escalation was defined as the occurrence of grade III-IV aGVHD within the first 100 days post-transplantation. The phase II stage comprised an expansion cohort, which was based on the optimal dose identified during phase I. aGvHD classification was established using the Mount Sinai Acute GVHD International Consortium (MAGIC) criteria, while chronic GvHD (cGvHD) was assessed per the latest National Institutes of Health Consensus on cGvHD. Patients were closely followed-up at +1, +2, +3, +4, +6, +9, +12, +18, and +24 months post-transplant. Results In the first stage, a total of 11 patients (5 in DL1, 3 in DL2, and 3 in DL3) were included, and no patient developed grade III-IV aGVHD. Based on this, DL3 was selected as the PTCy dose for phase II, which comprised 18 patients. Overall, 29 patients (17 females, 12 males) with a median age of 39 years (range 17-65) were included, and the median follow-up duration was 12.7 months (range 2.2-22.1). Patient and disease characteristics are summarized in Table 1. By day +30 post-ASCT, all patients achieved complete remission (CR) and minimal residual disease (MRD) clearance. No patient developed grade III-IV aGVHD within 100 days post-transplantation. There was no significant difference in the neutrophil and platelet engraftment interval among the three groups (Figure 1A, B). Among the 21 patients who received the DL3 dose of PTCy, the estimated cumulative incidence of grade II to IV aGVHD at day +100 was recorded at 28.6%, and the incidence of aGVHD at day +100 presented no difference among the three DL groups (Figure 1C). In addition, 1 patient in DL3 developed grade IV intestinal aGVHD on day +141 and died one month later. The estimated 1-year cumulative incidence of hemorrhagic cystitis (HC) and cytomegalovirus (CMV) reactivation was 19.3% and 19%, respectively (Figure 1D). Five patients (all in DL3) experienced relapse, with a median interval of 6.7 months and an estimated 1-year cumulative incidence of 10.6%. A total of 5 fatalities occurred during our study (1 in DL1, and 4 in DL3), 1 due to relapse, 2 from COVID-19-associated pulmonary aspergillosis, 1 from severe septicemia and 1 due to grade IV aGVHD as mentioned above. The estimated 6-month cumulative incidence of NRM was 9.5%, presenting no difference among the three DL groups (Figure 1E). Among the 20 evaluable patients, the estimated 1-year cumulative incidence of chronic GVHD (cGVHD) and moderate cGVHD was 37.3% and 16% (Figure 1F), respectively, with no severe cGVHD observed. No cases of patient relapse were reported. The estimated 1-year progression-free survival (PFS) and overall survival (OS) were 61.2% and 80.4%, respectively (Figure 1G). Conclusion The findings of this study substantiate that a two-day regimen of PTCy at 25 mg/kg/day serves as an effective and safe prophylactic measure against aGVHD, comparable to the standard dosing protocol. However, to definitively establish whether the de-escalated PTCy dosage provides superior outcomes to the standard regimen, longer-term follow-up and comparative studies are warranted.

Phase I / II Study on Infusion of Alloreactive or Ex Vivo il-15 Stimulated Natural Killer Cells after Haploidentical Stem Cell Transplantation in Pediatric Patients with Acute Leukemia (PHINK): A Study of the Spanish Hematopoietic Stem Cell Transplantation Group (GETH)

Background: Haploidentical hematopoietic stem cell transplantation (haplo-HSCT) is a highly complicated but effective procedure for high-risk pediatric leukemia in the absence of an HLA-identical donor. Post-transplant relapse is the main problem for patient survival. According to literature, Natural Killer (NK) cells play a potent role as inducers of the graft-versus-leukemia (GvL) effect in haplo-HSCT. The presence of alloreactive NK cells correlates with a lower relapse rate, improved engraftment, decreasing graft-versus-recipient disease (GvHD) and viral infection risk. In the absence of donor-recipient NK cell alloreactivity, other NK cell activation strategies are necessary. We propose a phase I/II clinical trial with dose escalation, multicenter, framed in the GETH, to determine dose-limiting toxicity (DLT) and the maximum tolerated dose (MTD) of a single infusion of alloreactive NK cells (Allo-NK) or NK cells stimulated ex vivo with IL-15 (IL15-NK) after haplo-HSCT in pediatric patients with high-risk leukemias. Methods: Eighteen pediatric patients with high-risk leukemia were recruited between September 16, 2020, and May 12, 2023, at 5 hospitals in Spain, Hospital Universitario La Paz, Hospital Universitario Gregorio Marañón, Hospital Universitario Niño Jesús, Hospital Universitario Central of Asturias and Hospital Santa Creu and Sant Pau. Patients were stratified in 2 treatment groups: Allo-NK (n=9) or IL15-NK (n=9), depending on the KIR disparity between donor and recipient. Our phase I/II clinical trial presents a dose-escalation design (3+3). The treatment cohorts are divided into cohort 1 (up to 2x10 7 cells/kg), cohort 2 (2-5x10 7 cells/kg) and cohort 3 (5-10x10 7 cells/kg). We have monitored infections reactivation, as well as, chimerism and engraftment after transplantation. In Allo-NK group, the KIR clone that provides alloreactivity in the NK cell was also tracked. The phenotypic profile and functional capacity of NK cells present in the patient up to 360 days after transplantation have also been analyzed. Results: Nine patients (4 in Allo-NK and 5 in IL-15NK) were included in cohort 1, 7 patients (4 in Allo-NK and 3 in IL-15NK) in cohort 2 and 2 patients (1 in Allo-NK and 1 in IL-15NK) in cohort 3. We were unable to complete the dose escalation design initially proposed due to the high weight of some patients and the unavailability of ex vivo expanded NK cells. In IL15-NK group patients presented a higher prevalence of B-ALL (p=0.018) and had received a previous transplant (p=0.082). NK cell infusions of IL15-NK group showed higher expression of CD25 and CD69 receptors and higher functional capacity. In the Allo-NK group, the most prevalent KIR-reactive clone was KIR2DL1 (55.6%). We also observed a tendency for KIR2DL1 alloreactive clone to increase from 30 (8,18%) to 360 (25,63%) days after transplantation. Regarding clinical outcomes in 2 study arms, the incidence of severe (Grades III-IV) acute GvHD was 22.2% and severe chronic GvHD was only observed in 1 (5.6%) patient (Table 1). The incidence any infection or endothelial vascular complications were 72% and 33% respectively. No statistical differences were observed in GvHD, infections and endothelial vascular complications. We found 2 relapses, 1 in each study arm (11.1%). Five patients died, 1 (5.6%) because of disease progression and 4 (22.2%) because transplant related complications (TRM) (Table 1). Dividing patients into the 3 dose-escalation cohorts, we found no significant differences between cohorts in the primary clinical outcomes analysed. One-years overall survival (OS) and disease-free survival (DFS) was 72.22% (CI95% 51.93-100) and GvHD-free/relapse-free survival (GRSF) was 64.1% (CI95% 44.62-92.1), finding no significant differences between either 2 study arms or the 3 dose-escalation cohorts. Regarding the analysis of the NK phenotype, we observed a tendency to increase the expression of CD16 and CD57 receptors between 30 to 360 days after transplantation in both groups. Conclusions: Two study arms shows similar data respect to clinical outcome. Patients infused with IL-15-stimulated NK cells showed similar toxicity to the alloreactive NK group. According to dose escalation, we observed no association between increased toxicity and increased number of infused NK cells. We were unfortunately unable to complete cohort 3 because of the cells/kg ratio in some patients.

Disturbance in the reconstitution of distinct T-cell subsets and the incidence of GvHD following allo-HSCT in pediatric patients with non-malignant hematological disorders

BackgroundThe reconstitution of different T-cell subsets following allogeneic hematopoietic stem cell transplantation (allo-HSCT) is critical for efficient pathogen protection and the prevention of graft-versus-host disease (GvHD). In particular, studies have highlighted the importance of balanced ratios of regulatory T-cells (Tregs) and distinct functionally T-cells in preventing acute and chronic GvHD. MethodsWe evaluated the regeneration of CD4 and CD8 T-cell subpopulations in nine pediatric patients with non-malignant disorders following allo-HSCT from a fully HLA-identical donor. ResultsCD4 and CD8 T-cells were higher 12 months after the transplant but still lower than in healthy controls and pre-transplant. However, we found after allo-HSCT, central memory and effector memory cell subsets were the predominant phenotypes in the CD4 and CD8 T-cell populations, respectively. In patients who had developed acute GvHD, there was an increase in the frequency of TEMRA (effector memory T cells that re-express CD45RA) cells within the CD4 T-cell population. Meanwhile, in patients with chronic GvHD, we observed a decrease in Th1 cells in CD4 T-cells and effector memory cells within the CD8 T-cell population. In addition, we found decreased TEMRA cell subsets in CD4 and CD8 T-cell populations in chronic GvHD. ConclusionOur findings suggest a possible relationship between the influence of acute GvHD and its prevention on delayed CD4 T-cell reconstitution and, reciprocally, unbalanced regeneration of CD4 and CD8 T-cell subsets in the development of chronic GvHD.

Acute graft-versus-host disease after allogeneic stem cell transplantation from a haploidentical donor with post-transplant cyclophosphamide administration

Allogeneic hematopoietic stem cell transplantation is the only curative treatment for many life-threatening diseases. Due to the difficulty of finding an HLA-identical donor, transplantation from a haploidentical donor has become a frequent alternative. This option is associated with a higher risk of graft-versus-host disease (GVHD). In this article, we present the current view on the pathogenesis, treatment and prevention of GVHD and report a clinical case of acute GVHD after allogeneic hematopoietic stem cell transplantation from a haploidentical donor with post-transplant cyclophosphamide prophylaxis. The patient's parents gave consent to the use of their child's data, including photographs, for research purposes and in publications.

Clinical Benefit of Low-Dose Antithymocyte Globulin-Thymoglobulin as Graft-versus-Host Disease Prophylaxis in Patients Receiving Allogeneic Peripheral Blood Stem Cell Transplantation from HLA-Identical Donors

Graft-versus-host disease (GVHD) is a major complication of allogeneic peripheral blood stem cell transplantation (PBSCT). Previous randomized studies have already shown that several types of antihuman T-lymphocyte immune globulin (ATG) as GVHD prophylaxis can reduce the incidence of acute GVHD and chronic GVHD. However, the efficacy and safety of PBSCT from human leukocyte antigen (HLA)-identical donors with low-dose ATG remain unclear. This study aimed to clarify the efficacy and safety of PBSCT from HLA-identical donors with low-dose ATG compared to PBSCT from HLA-identical donors without ATG. We retrospectively analyzed the outcomes of allogeneic PBSCT from HLA-identical donors with low-dose ATG-thymoglobulin (ATG-T: 2.5 mg/kg) versus PBSCT without ATG-T. Patients' data were collected retrospectively from the medical records of Anjo Kosei Hospital. This study was conducted from 2009 to the final follow-up in October 2022. In total, 47 of 91 patients received ATG-T between January 2009 and March 2020. ATG-T reduced the incidence of moderate-to-severe chronic GVHD (hazard ratio [HR]: 0.15, 95% confidence interval [CI]: 0.057-0.41, p < 0.0010) and non-relapse mortality (HR: 0.21, 95% CI: 0.0058-0.75, p = 0.016) without increasing the risk of relapse. The overall survival did not differ significantly between the two groups. However, the low-dose ATG-T group had better moderate-to-severe chronic GVHD-free, relapse-free survival rates (HR: 0.47, 95% CI: 0.27-0.80, p = 0.0054) than the non-ATG-T group. In addition, the multistate analysis revealed that the low-dose ATG-T group had better current GVHD-free, relapse-free survival at 24 months after transplantation than the non-ATG group (45% [95% confidence interval, CI: 29%-63%) and 21% (95% CI: 9.1%-34%)], respectively, p = 0.015). Low-dose ATG-T did not increase the incidence of infections and adverse events. Low-dose ATG-T could be beneficial for patients receiving PBSCT from HLA-identical donors.

Impact of Conditioning Regimen and Graft-versus-Host Disease Prophylaxis on The Outcome of Haploidentical Peripheral Blood Stem Cell Transplantation for High-Risk Severe Aplastic Anemia in Children and Young Adults: A Report from the Pediatric Severe Aplastic Anemia Consortium of India

Allogenic hematopoietic cell transplantation (HCT) is the best curative approach for patients with severe aplastic anemia (SAA). The outcomes of HCT from haploidentical family donors (HFDs) have improved, making it a feasible option for patients lacking an HLA-identical donor. However, data on HFD-HCT for younger patients with SAA is sparse. In this multicenter retrospective study, we evaluated the outcomes of 79 patients undergoing HFD-HCT for SAA. All the patients were heavily pretransfused, the median time to HCT was >12 months, and 67% had failed previous therapies. Conditioning was based on fludarabine (Flu)-cyclophosphamide (Cy)-antithymocyte globulin (ATG)/total body irradiation (TBI) with or without thiotepa/melphalan (TT/Mel). Post-transplantation Cy (PTCy) and calcineurin inhibitors (CNIs)/sirolimus were used as graft-versus-host disease (GVHD) prophylaxis with or without abatacept. The rate of primary graft failure (PGF) was 16.43% overall, lower in patients conditioned with TT/Mel. The incidences of acute and chronic GVHD were 26.4% and 18.9%, respectively. At a median follow-up of 48 months, the overall survival (OS) and event-free survival (EFS) were 61.6% and 58.1%, respectively. Both OS and EFS were better in the TT/Mel recipients and with abatacept as GVHD prophylaxis. On multivariate analysis, the use of abatacept was found to favorably impact the outcome variables, including GVHD and EFS. Our study suggests that PTCy-based HFD-HCT is a reasonable option for young patients with high-risk SAA, in whom optimization of conditioning and GVHD prophylaxis might further improve outcomes.

Amylose AA vésicale : une localisation rare. À propos d’un cas

IntroductionBladder localization of AA amyloidosis is rare. It can be responsible for massive and recurrent hematuria. We report a case of bladder AA amyloidosis secondary to Crohn's disease in a renal transplant patient. Clinical observationA 62-year-old man, suffering from Crohn's disease since 1991 complicated by renal AA amyloidosis. He received a kidney transplant since 20 years from an HLA identical donor. After an 18-year period of clinical remission, the patient was admitted for a flare-up of his Crohn's disease in the form of intermittent diarrhoea. Treatment with corticosteroids allowed a good evolution. A year later, he was rehospitalized for massive macroscopic haematuria. Histological examination of the bladder biopsy revealed AA amyloidosis. The patient fully recovered but died 6 weeks later from septic shock of urinary origin. ConclusionThe treatment of bladder localization of AA amyloidosis is based on treating the cause. Hematuria is sometimes massive, exceptionally requiring emergency cystectomy for haemostasis.

Allogeneic Hematopoietic Cell Transplantation (Allo-HCT) in Patients with Calr-Mutated Myelofibrosis

Background: Between 50-65% of myelofibrosis (MF) patients who undergo allogeneic hematopoietic cell transplantation (allo-HCT) are cured. Patient age, performance status, comorbidities, donor type, and HLA compatibility are established risk factors for allo-HCT outcomes. However, prognostic information after transplant in MF is largely based on JAK2-mutated patients, as this molecular abnormality is by far the most common and the first to be described. Since there is evidence suggesting that CALR-mutated patients could have a better outcome (Kroger et al., BBMT 2017), a study evaluating prognostic factors in this specific molecular subtype may be of clinical interest. Method: This is a retrospective, registry-based study approved by the Chronic Malignancies Working Party (CMWP) of the European Society for Blood and Marrow Transplantation (EBMT). For the present study, inclusion criteria were adult patients with CALR-mutated MF undergoing first allo-HCT between 2005 and 2019. Patients transplanted from umbilical cord blood or with history of leukemic transformation were excluded. Primary study outcomes were OS, progression-free survival (PFS), relapse, non-relapse mortality (NRM) and graft-versus-host disease (GVHD)-free and relapse-free survival (GRFS). Results: 346 patients transplanted in 123 centers were included, of whom 207 (59.8%) were male. A total of 244 (70.5%) patients had primary MF (PMF) and 102 patients had MF secondary to prior essential thrombocythemia (SMF). Median interval from diagnosis to allo-HCT was 50.9 months (IQR: 17.2-155.6). Median age was 57.4 years (IQR: 51.2-63). DIPSS score at time of allo-HCT was available in 256 (74%) patients and was high, intermediate-2, intermediate-1 and low in 17%, 46%, 35%, and 2%, respectively. Sixty-nine patients (21%) had a high comorbidity index (HCT-CI) > 3. Seventeen patients (7.5%) had been splenectomized before transplant. Reduced intensity (RIC) regimens were utilized in 63% of patients and the donor source was peripheral blood in 95% of cases. Regarding donor type, an HLA-matched sibling donor (MSD), mismatched related donor (MMRD), matched unrelated donor (MUD) and mismatched unrelated donor (MMUD) was used in 92 (27%), 18 (5%), 167 (48%) and 48 (14%) of patients, respectively. T cell depletion was used in 77% of patients. Median time to neutrophil engraftment was 17 days. Incidence of acute GVHD grades II-IV at 100 days and extensive chronic GVHD at 60 months were 27% and 28%, respectively. After a median follow-up of 40 months from transplant, the estimated 5-year OS rate, PFS, GRFS, NRM and relapse incidence was 63%, 57%, 35%, 25% and 18%, respectively. Causes of death were relapse/progression (n=11), GVHD (n=36), infection (n=27), organ failure/toxicity (n=11), secondary malignancy (n=6), other (n=9), and unknown (n=3). The estimated 3-year OS rate was 79%, 37%, 72% and 62% for allo-HCT from MSD, MMRD, MUD and MMUD, respectively (p=0.09; Figure 1). The estimated 5-year OS rate in patients transplanted from an HLA identical donor was 64%. In univariable analysis, a high comorbidity index (47% vs. 66%; p=0.013) and a PMF diagnosis (55% vs. 79%; p=0.008) correlated with inferior 5-year OS rate. These two factors were associated with higher NRM rate at 5 years after transplant (HCT-CI > 3: 28% vs. 19%, p=0.033; PMF: 31% vs. 12%, p=0.012), with no difference in relapse incidence. Table 1 shows the results of the multivariable analyses for the main outcomes. As can be seen, older age (HR: 1.37, 95% CI: 1.08-1.74; p=0.009) was the only factor significantly associated with a worse OS, whereas PMF (HR: 1.58, 95% CI: 0.96-2.62; p=0.07) and transplant from a mismatched donor (HR: 1.55, 95% CI: 0.95-2.52; p=0.08) had a near-to-significant trend for decreased OS. Conclusion: this is the largest series of allo-HCT for CALR-mutated MF patients. Overall, the results seem favorable, especially in patients with SMF or transplanted from an HLA-identical donor, where the 5-year OS in this multicenter series was 79% and 64%, respectively. NRM was the main cause of treatment failure. Figure 1. Overall survival after transplant in 346 CALR-positive myelofibrosis patients depending on the donor type. Table 1. Results of the multivariable analyses for the main study outcomes. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal