Impact of hematopoietic cell transplantation on myocardial fibrosis in young patients with sickle cell disease.

ABSTRACT: Serial cardiovascular magnetic resonance evaluation of children and young adults with SCD who underwent hematopoietic cell transplantation showed mean ECV, representing diffuse myocardial fibrosis, decreased 3.4% from baseline to 12 months posttransplantation. This trial was registered at www.clinicaltrials.gov as #NCT04362293.

Safety and Efficacy of High-Dose Memory CD45RO+ Donor Lymphocyte Infusion in Pediatric Recipients after Hematopoietic Stem Cell Transplantation.

Memory T selected cells (CD45RA-/RO+) as donor lymphocyte infusion are less capable of producing alloreactivity and graft versus host disease (GvHD) compared with naïve T cells. The objective of this study was to evaluate the safety and efficacy of high-dose memory (CD45RA-/RO+) donor lymphocyte infusion (mDLI) after allogeneic hematopoietic cell transplantation (HCT). Indications for mDLI were "as needed" and "as prophylactic regimen." Sixty-one children diagnosed with malignant (82%) and non-malignant diseases (18%) received 241 mDLIs. Patients received a median of three infusions (range 1‒13) of mDLI with a median infused dose of 1.35 × 107/kg CD45RO+ containing 8.96 × 106/kg CD3+CD45RO+ and 3.81 × 103/kg CD3+CD45RA+. De novo GvHD developed in 7 patients following 4% of the mDLI infusions. Among patients with GvHD before mDLI, this condition worsened following 6 infusions (11%) in the 3 patients with grade II-IV acute GvHD. A decrease in cytomegalovirus viral load followed 65% of mDLI infusions. Two-year overall survival (OS) for the total cohort was 64% (95% CI 57%‒72%). For patients receiving prophylactic mDLI, the two-year non-relapse mortality was 10% (95% CI 9%‒11%). In summary, high-dose mDLI is feasible and safe, with a relatively low risk of severe GvHD even in patients with active GvHD. Importantly, mDLI was associated with positive effects, including enhanced control of CMV viremia.

Blinatumomab infusion interruptions in pediatric patients rarely lead to readmission.

Blinatumomab is a bispecific T-cell engager administered as a 28-day continuous infusion. Infusions can be associated with interruptions requiring support from clinical staff, but the frequency of interventions with outpatient blinatumomab has not been characterized. This study is a single-center, retrospective review of patients who received blinatumomab between December 3, 2014 and October 31, 2021 to determine frequency and type of interventions. Forty patients received blinatumomab for 69 cycles. Clinical staff intervention was required in 31 (45%) cycles, only six (8.7%) cycles needed readmission. Management of outpatient blinatumomab infusions requires education and training of clinical staff and caregivers to quickly troubleshoot interruptions.

Acute kidney injury following treatment with CD19-specific CAR T-cell therapy in children, adolescent, and young adult patients with B-cell acute lymphoblastic leukemia.

BACKGROUND: CD19-specific chimeric antigen receptor (CAR) T-cell therapy has shown promising disease responses in patients with high-risk B-cell malignancies. However, its use may be related to complications such as immune-mediated complications, infections, and end-organ dysfunction. The incidence of post-CAR T-cell therapy acute kidney injury (AKI) in the children, adolescent, and young adult (CAYA) patient population is largely unreported. METHODS: The objectives of this study were to determine the incidence of AKI in CAYA patients with high-risk B-cell malignancies treated with CD19-CAR T-cell therapy, evaluate potential risk factors for developing AKI, and determine patterns of kidney function recovery. We conducted a retrospective analysis of 34 CAYA patients treated with CD19-CAR T-cell at a single institution. RESULTS: There was a cumulative incidence of any grade AKI by day 30 post-infusion of 20% (n = 7), with four cases being severe AKI (stages 2-3) and one patient requiring kidney replacement therapy. All episodes of AKI developed within the first 14 days after receiving CAR T-cell therapy and 50% of patients with AKI recovered kidney function to baseline within 30 days post-infusion. No evaluated pre-treatment risk factors were associated with the development of subsequent AKI; there was an association between AKI and cytokine release syndrome and neurotoxicity. We conclude that the risk of developing AKI following CD19-CAR T-cell therapy is highest early post-infusion, with most cases of AKI being severe. CONCLUSIONS: Frequent monitoring to facilitate early recognition and subsequent management of kidney complications after CD19-CAR T-cell therapy may reduce the severity of AKI in the CAYA patient population.

Microbiota Predict Infections and Acute Graft-Versus-Host Disease After Pediatric Allogeneic Hematopoietic Stem Cell Transplantation.

BACKGROUND: Despite preventive measures, infections continue to pose significant risks to pediatric allogeneic hematopoietic cell transplantation (allo-HCT) recipients. The gut microbiota has been linked to clinical outcomes following adult allo-HCT. This study evaluated whether similar disruptions or differing microbiota patterns were associated with infection risk in pediatric allo-HCT. METHODS: In a prospective observational study, fecal samples were obtained from 74 children before conditioning and upon neutrophil recovery. Microbiome signatures identified through sequencing were examined for their associations with infections or acute graft-versus-host disease (aGVHD) in the first-year post-HCT using Cox proportional hazards analysis. RESULTS: Microbiome disruption in adults, did not predict infection risk in pediatric allo-HCT. Unique microbiota signatures were associated with different infections or aGVHD. A ratio of strict and facultative anaerobes (eg, Lachnoclostridium, Parabacteroides) prior to conditioning predicted bacteremia risk (Cox hazard ratio [HR], 3.89). A distinct ratio of oral (eg, Rothia, Veillonella) to intestinal anaerobes (eg, Anaerobutyricum, Romboutsia) at neutrophil recovery predicted likelihood of bacterial infections (Cox HR, 1.81) and viral enterocolitis (Cox HR, 1.96). CONCLUSIONS: Interactions between medical interventions, pediatric hosts, and microbial communities contribute to microbiota signatures that predict infections. Further multicenter study is necessary to validate the generalizability of these ratios as biomarkers.

Development of a cGMP-compliant process to manufacture donor-derived, CD45RA-depleted memory CD19-CAR T cells.

Autologous chimeric antigen receptor (CAR) T cells targeting the CD19 antigen have demonstrated a high complete response rate in relapsed/refractory B-cell malignancies. However, autologous CAR T cell therapy is not an option for all patients. Here we optimized conditions for clinical-grade manufacturing of allogeneic CD19-CAR T cells using CD45RA-depleted donor memory T cells (Tm) for a planned clinical trial. Tm were activated using the MACS GMP T Cell TransAct reagent and transduced in the presence of LentiBOOST with a clinical-grade lentiviral vector that encodes a 2nd generation CD19-CAR with a 41BB.zeta endodomain. Transduced T cells were transferred to a G-Rex cell culture device for expansion and harvested on day 7 or 8 for cryopreservation. The resulting CD19-CAR(Mem) T cells expanded on average 34.2-fold, and mean CAR expression was 45.5%. The majority of T cells were CD4+ and had a central memory or effector memory phenotype, and retained viral specificity. CD19-CAR(Mem) T cells recognized and killed CD19-positive target cells in vitro and had potent antitumor activity in an ALL xenograft model. Thus we have successfully developed a current good manufacturing practice-compliant process to manufacture donor-derived CD19-CAR(Mem) T cells. Our manufacturing process could be readily adapted for CAR(Mem) T cells targeting other antigens.

A validated pediatric disease risk index for allogeneic hematopoietic cell transplantation.

A disease risk index (DRI) that was developed for adults with hematologic malignancy who were undergoing hematopoietic cell transplantation is also being used to stratify children and adolescents by disease risk. Therefore, to develop and validate a DRI that can be used to stratify those with AML and ALL by their disease risk, we analyzed 2569 patients aged <18 years with acute myeloid (AML; n = 1224) or lymphoblastic (ALL; n = 1345) leukemia who underwent hematopoietic cell transplantation. Training and validation subsets for each disease were generated randomly with 1:1 assignment to the subsets, and separate prognostic models were derived for each disease. For AML, 4 risk groups were identified based on age, cytogenetic risk, and disease status, including minimal residual disease status at transplantation. The 5-year leukemia-free survival for low (0 points), intermediate (2, 3, 5), high (7, 8), and very high (>8) risk groups was 78%, 53%, 40%, and 25%, respectively (P < .0001). For ALL, 3 risk groups were identified based on age and disease status, including minimal residual disease status at transplantation. The 5-year leukemia-free survival for low (0 points), intermediate (2-4), and high (≥5) risk groups was 68%, 51%, and 33%, respectively (P < .0001). We confirmed that the risk groups could be applied to overall survival, with 5-year survival ranging from 80% to 33% and 73% to 42% for AML and ALL, respectively (P < .0001). This validated pediatric DRI, which includes age and residual disease status, can be used to facilitate prognostication and stratification of children with AML and ALL for allogeneic transplantation.

Comparison of Haemonetics Cell Saver 5+ and manual density separation for optimum depletion of red blood cells and preservation of CD34+ cells in major ABO-incompatible bone marrow grafts.

BACKGROUND AIMS: The current approach for preventing hemolysis of red blood cells (RBCs) in major ABO-incompatible bone marrow (BM) grafts after infusion is to deplete RBCs from BM products before transplantation. Traditionally, manual density separation (MDS) using Ficoll-Hypaque (Cytiva Sweden AB, Uppsala, Sweden has been used to accomplish RBC depletion. This process yields good CD34+ cell recovery, but it requires open manipulation and is labor-intensive and time-consuming. We hypothesized that an alternative automated method using Haemonetics Cell Saver 5+ (Haemonetics Corporation, Boston, MA, USA) would offer equivalent RBC depletion and CD34+ cell recovery. Small marrow volumes from pediatric donors can be processed using Cell Saver (CS) without adding the third-party RBCs necessary for other automated methods. METHODS: This retrospective analysis comprised data from 58 allogeneic BM grafts. RBC depletion and CD34+ cell recovery from BM using MDS (35 grafts) were compared with CS (14 grafts). Nine products underwent RBC depletion using CS with Ficoll (CS-F) when RBC volume was less than 125 mL. RESULTS: Linear regression analysis of log transformation of CD34+ cell recovery adjusted for log transformation of both baseline CD34+ cell content and baseline total volume showed no significant difference between MDS and CS (estimated coefficient, -0.121, P = 0.096). All products contained an RBC volume of less than 0.25 mL/kg post-processing. CD34+ cell recovery with CS-F was comparable to MDS and CS and suitable for pediatric recipients of allogeneic hematopoietic cell transplantation. CONCLUSIONS: We provide evidence that an automated method using Haemonetics Cell Saver 5+ achieves RBC depletion and CD34+ cell recovery comparable to MDS when adjusting for baseline factors.

Allogeneic CD34+ selected hematopoietic stem cell boost following CAR T-cell therapy in a patient with prolonged cytopenia and active infection.

Hematological toxicity (hematotoxicity) leading to peripheral cytopenias is a common long-term adverse effect following the use of CD19-chimeric antigen receptor (CD19-CAR) T-cell therapies. However, management remains unclear for patients whose cytopenias persist beyond 1 month after CAR T-cell infusion. We present the case of a 21-year old who received CD19-CAR T-cell therapy for relapse following a haploidentical transplant. He developed hematotoxicity and consequently multiple life-threatening infections. We administered a CD34+ hematopoietic stem cell boost (HSCB) from his transplant donor, which led to hematopoietic recovery and resolution of his infections without any effect on the activity of CD19-CAR T cells. CD34+ HSCB can be a safe and effective option to treat hematotoxicity following CD19-CAR T-cell therapy.

Outcomes following intolerance to calcineurin inhibitor-based graft-versus-host disease prophylaxis in children after allogeneic hematopoietic cell transplantation.

Calcineurin inhibitors (CNI), cyclosporine and tacrolimus, are commonly used for pharmacologic prophylaxis of graft-versus-host disease after allogeneic hematopoietic cell transplantation (HCT). Unfortunately, their use is associated with significant toxicities. While intolerance to CNI is well defined, there is very little information on how they impact outcomes after HCT in children. Our retrospective study in a cohort of 82 children shows a high intolerance rate of 39% in this population associated with lower event-free survival and a higher transplant-related mortality.

Primary hypothyroidism in childhood cancer survivors: Prevalence, risk factors, and long-term consequences.

BACKGROUND: Data on primary hypothyroidism and its long-term impact on the health, cognition, and quality of life (QOL) of childhood cancer survivors are limited. This study examined the prevalence of and risk factors for primary hypothyroidism and its associations with physical, neurocognitive, and psychosocial outcomes. METHODS: This was a retrospective study with a cross-sectional health outcome analysis of an established cohort comprising 2965 survivors of childhood cancer (52.8% male; median current age, 30.9 years, median time since cancer diagnosis, 22.3 years). Multivariable logistic regression estimated odds ratios (ORs) and 95% confidence intervals (CIs) for associations between primary hypothyroidism and cancer-related risk factors, cardiovascular disease risk factors, frailty, neurocognitive and QOL outcomes, social attainment, and subsequent thyroid carcinoma. Associations between serum free thyroxine and thyrotropin levels at assessment and health outcomes were explored. RESULTS: The prevalence of primary hypothyroidism was 14.7% (95% CI, 13.5%-16.0%). It was more likely in females (OR, 1.06; 95% CI, 1.03-1.08), was less likely in non-Whites (OR, 0.96; 95% CI, 0.93-0.99), was associated with thyroid radiotherapy (higher risk at higher doses), and was more common if cancer was diagnosed at an age ≥ 15.0 years versus an age < 5 years (OR, 1.05; 95% CI, 1.01-1.09). Primary hypothyroidism was associated with frailty (OR, 1.54; 95% CI, 1.05-2.26), dyslipidemia (OR, 1.52; 95% CI, 1.14-2.04), impaired physical QOL (OR, 1.66; 95% CI, 1.12-2.48), and having health care insurance (OR, 1.51; 95% CI, 1.07-2.12). CONCLUSIONS: Primary hypothyroidism is common in survivors and is associated with unfavorable physical health and QOL outcomes. The impact of thyroid hormone replacement practices on these outcomes should be investigated further.

Lentiviral Gene Therapy Combined with Low-Dose Busulfan in Infants with SCID-X1.

BACKGROUND: Allogeneic hematopoietic stem-cell transplantation for X-linked severe combined immunodeficiency (SCID-X1) often fails to reconstitute immunity associated with T cells, B cells, and natural killer (NK) cells when matched sibling donors are unavailable unless high-dose chemotherapy is given. In previous studies, autologous gene therapy with γ-retroviral vectors failed to reconstitute B-cell and NK-cell immunity and was complicated by vector-related leukemia. METHODS: We performed a dual-center, phase 1-2 safety and efficacy study of a lentiviral vector to transfer IL2RG complementary DNA to bone marrow stem cells after low-exposure, targeted busulfan conditioning in eight infants with newly diagnosed SCID-X1. RESULTS: Eight infants with SCID-X1 were followed for a median of 16.4 months. Bone marrow harvest, busulfan conditioning, and cell infusion had no unexpected side effects. In seven infants, the numbers of CD3+, CD4+, and naive CD4+ T cells and NK cells normalized by 3 to 4 months after infusion and were accompanied by vector marking in T cells, B cells, NK cells, myeloid cells, and bone marrow progenitors. The eighth infant had an insufficient T-cell count initially, but T cells developed in this infant after a boost of gene-corrected cells without busulfan conditioning. Previous infections cleared in all infants, and all continued to grow normally. IgM levels normalized in seven of the eight infants, of whom four discontinued intravenous immune globulin supplementation; three of these four infants had a response to vaccines. Vector insertion-site analysis was performed in seven infants and showed polyclonal patterns without clonal dominance in all seven. CONCLUSIONS: Lentiviral vector gene therapy combined with low-exposure, targeted busulfan conditioning in infants with newly diagnosed SCID-X1 had low-grade acute toxic effects and resulted in multilineage engraftment of transduced cells, reconstitution of functional T cells and B cells, and normalization of NK-cell counts during a median follow-up of 16 months. (Funded by the American Lebanese Syrian Associated Charities and others; LVXSCID-ND ClinicalTrials.gov number, NCT01512888.).

"Giving the gift of life twice": Understanding the lived experiences of parent donors and nondonors in pediatric haploidentical hematopoietic cell transplantation.

BACKGROUND: The use of parental donors in pediatric haploidentical hematopoietic cell transplantation is increasing, but research on the psychosocial impact of parental donation is currently limited. OBJECTIVES: As part of a larger study, we conducted a retrospective, qualitative analysis to explore parental perceptions of the donation process and the impact of being a donor (or nondonor) on parents' adjustment and coping with their child's transplant experience. METHODS: Parents/caregivers of children who underwent transplantation with a parental donor or a matched unrelated donor (N = 136) participated in interviews and completed an open-ended questionnaire. RESULTS: Six themes were identified in the data: level of understanding and satisfaction; perception of choice; preparation for donation; perceptions of donation and infusion; benefit finding; and psychological impact of transplantation. Most parents were satisfied with the information they received and reported a good understanding of transplantation and donation procedures. Parents were divided on perspectives of choice, but their responses reflect that the necessity of saving their child's life does not allow for choice. They described considerable effort to prepare for transplantation, physically, emotionally, and logistically. Parents acknowledged the psychological impact while identifying positive outcomes that resulted from their child's transplant journey. CONCLUSIONS: Results highlight the unique experiences of parental donors and nondonors from the anticipation phase to the completion of their child's transplant. Additionally, findings inform supportive care guidance by highlighting the need to assess parental donors' emotional functioning, provide support post donation, and conduct bereavement follow-up.

Hemophagocytic lymphohistiocytosis-like toxicity (carHLH) after CD19-specific CAR T-cell therapy.

Chimeric antigen receptor T-cell (CAR T-cell) therapy is associated with significant toxicities secondary to immune activation, including a rare but increasingly recognised severe toxicity resembling haemophagocytic lymphohistiocytosis (carHLH). We report the development of carHLH in 14·8% of paediatric patients and young adults treated with CD19-specific CAR T-cell therapy with carHLH, occurring most commonly in those with high disease burden. The diagnosis and treatment of carHLH required a high index of suspicion and included multidrug immunomodulation with variable response to therapies. Compared to patients without carHLH, patients with carHLH had both reduced response to CAR T-cell therapy (P-value = 0·018) and overall survival (P-value = < 0·0001).

Reduced-intensity conditioning-based hematopoietic cell transplantation for dyskeratosis congenita: Single-center experience and literature review.

BACKGROUND: Bone marrow failure in dyskeratosis congenita (DKC) is progressive, and allogeneic hematopoietic cell transplantation (HCT) is the only curative treatment. However, outcomes after HCT are suboptimal because of mucosal, vascular, pulmonary, and hepatic fragility, which can be exacerbated by chemotherapy conditioning and graft-versus-host disease (GVHD). These toxicities can be mitigated by reducing the intensity of the conditioning regimen. PROCEDURES: We performed a retrospective analysis on pediatric patients with DKC who underwent HCT at our institution between 2008 and 2019. RESULTS: We identified nine patients (median age, 5.7 years) who underwent HCT with a fludarabine-based reduced-intensity conditioning (RIC) regimen. GVHD prophylaxis consisted of tacrolimus plus mycophenolate mofetil (MMF) (n  =  8), tacrolimus/pentostatin (n  =  1), or cyclosporine/MMF (n  =  1). The median time to neutrophil engraftment was 19 days (range, 13-26 days), and the median time to platelet engraftment was 18 days (range, 17-43 days). Lung function, as measured by spirometry in six patients, remained stable during post-HCT observation. Six patients (67%) remain alive, with a median follow-up of 73.5 months. CONCLUSION: Because of toxicity after myeloablative conditioning, RIC is becoming standard for HCT in DKC. These results suggest that RIC regimen is feasible and safe for patients with DKC and does not accelerate pulmonary damage in the short-to-medium term after HCT.

Targeting plasma cells with daratumumab aids in the treatment of post-transplant autoimmune-like hepatitis.

Antibody-mediated autoimmune-like hepatitis is a rare and challenging occurrence after hematopoietic cell transplant (HCT). We present the case of a 16-year-old male patient with Ph+ ALL who underwent matched sibling donor HCT and developed autoimmune-like hepatitis after receiving ponatinib for post-HCT maintenance, evidenced by marked plasma cell infiltrate on liver biopsy. He was successfully treated with steroids and daratumumab, an anti-CD38-monoclonal antibody. The dramatic response in this patient warrants expanded investigation of daratumumab for plasma cell-mediated disorders post-HCT. It further highlights that identifying mechanisms of immune-mediated injury can allow for directed therapy and limit exposure to broad immune suppression.

Hematopoietic cell transplant for reversal of liver fibrosis in a pediatric patient with erythropoietic protoporphyria.

BACKGROUND: EPP is a rare disorder of heme biosynthesis in which patients present with disabling photosensitivity. A subset of patients develop severe liver disease with progressive liver failure necessitating an OLT. A HCT can potentially cure EPP by replacing the native bone marrow, which is the primary site of heme synthesis. However, due to concerns for inherent risks of treatment-related toxicities, the use of HCT has been reserved for patients undergoing an OLT to avoid disease recurrence in the hepatic graft. Data for HCT in EPP are lacking, particularly in the pediatric population. CASE (METHODS/RESULTS): We present the case of a 12-year-old patient with EPP photosensitivity and cirrhosis, whom we successfully treated with pre-emptive allogeneic HCT, significantly improving the patient's quality of life. We used a matched-unrelated donor bone marrow-derived graft. Our patient achieved full donor peripheral blood chimerism and has not had any evidence of GVHD. In addition to resolution of photosensitivity, our patient had reversal of liver fibrosis which we feel was largely due to intervention at an early stage of compensated cirrhosis. CONCLUSION: Our case highlights the successful application of a known RIC regimen to this rare disorder that was well tolerated with sustained donor engraftment. It also emphasizes the importance of timing for HCT in patients with EPP and liver fibrosis. HCT should be considered early in pediatric patients with EPP-hepatopathy to prevent progression to liver failure and need for OLT with lifelong immunosuppression.

Nasal Wash Cytokines during Respiratory Viral Infection in Pediatric Allogeneic Hematopoietic Cell-Transplant Recipients.

Allogeneic hematopoietic cell-transplant (alloHCT) recipients are at increased risk of complications from viral respiratory-tract infections (vRTIs). We measured cytokine concentrations in nasal washes (NWs) from pediatric alloHCT recipients to better understand their local response to vRTI. Forty-one immunologic analytes were measured in 70 NWs, collected during and after vRTI, from 15 alloHCT recipients (median age, 11 yr) with 19 episodes of vRTI. These were compared with NW cytokine concentrations from an independent group of otherwise healthy patients. AlloHCT recipients are able to produce a local response to vRTI and produce IFN-α2 and IL-12p40 in significant quantities above an uninfected baseline early in infection. Compared with otherwise healthy comparator-group patients, alloHCT recipients have higher NW concentrations of IL-4 when challenged with vRTI. Further study of these immunologic analytes as well as of type 1 versus type 2 balance in the respiratory mucosa in the context of vRTI during immune reconstitution may be of future research interest in this vulnerable patient population.

Outcomes of Hematopoietic Cell Transplantation in Patients with Germline SAMD9/SAMD9L Mutations.

Germline mutations in SAMD9 and SAMD9L genes cause MIRAGE (myelodysplasia, infection, restriction of growth, adrenal hypoplasia, genital phenotypes, and enteropathy) (OMIM: *610456) and ataxia-pancytopenia (OMIM: *611170) syndromes, respectively, and are associated with chromosome 7 deletions, myelodysplastic syndrome (MDS), and bone marrow failure. In this retrospective series, we report outcomes of allogeneic hematopoietic cell transplantation (HCT) in patients with hematologic disorders associated with SAMD9/SAMD9L mutations. Twelve patients underwent allogeneic HCT for MDS (n = 10), congenital amegakaryocytic thrombocytopenia (n = 1), and dyskeratosis congenita (n = 1). Exome sequencing revealed heterozygous mutations in SAMD9 (n = 6) or SAMD9L (n = 6) genes. Four SAMD9 patients had features of MIRAGE syndrome. Median age at HCT was 2.8 years (range, 1.2 to 12.8 years). Conditioning was myeloablative in 9 cases and reduced intensity in 3 cases. Syndrome-related comorbidities (diarrhea, infections, adrenal insufficiency, malnutrition, and electrolyte imbalance) were present in MIRAGE syndrome cases. One patient with a familial SAMD9L mutation, MDS, and morbid obesity failed to engraft and died of refractory acute myeloid leukemia. The other 11 patients achieved neutrophil engraftment. Acute post-transplant course was complicated by syndrome-related comorbidities in MIRAGE cases. A patient with SAMD9L-associated MDS died of diffuse alveolar hemorrhage. The other 10 patients had resolution of hematologic disorder and sustained peripheral blood donor chimerism. Ten of 12 patients were alive with a median follow-up of 3.1 years (range, 0.1 to 14.7 years). More data are needed to refine transplant approaches in SAMD9/SAMD9L patients with significant comorbidities and to develop guidelines for their long-term follow-up.

Outcomes after Second Hematopoietic Cell Transplantation in Children and Young Adults with Relapsed Acute Leukemia.

Children with acute leukemia who relapse after hematopoietic cell transplantation (HCT) have few therapeutic options. We studied 251 children and young adults with acute myelogenous or lymphoblastic leukemia who underwent a second HCT for relapse after their first HCT. The median age at second HCT was 11 years, and the median interval between first and second HCT was 17 months. Most of the patients (n = 187; 75%) were in remission, received a myeloablative conditioning regimen (n = 157; 63%), and underwent unrelated donor HCT (n = 230; 92%). The 2-year probability of leukemia-free survival (LFS) was 33% after transplantation in patients in remission, compared with 19% after transplantation in patients not in remission (P = .02). The corresponding 8-year probabilities were 24% and 10% (P = .003). A higher rate of relapse contributed to the difference in LFS. The 2-year probability of relapse after transplantation was 42% in patients in remission and 56% in those in relapse (P = .05). The corresponding 8-year probabilities were 49% and 64% (P = .04). These data extend the findings of others showing that patients with a low disease burden are more likely to benefit from a second transplantation. Late relapse led to a 10% decrement in LFS beyond the second year after second HCT. This differs from first HCT, in which most relapses occur within 2 years after HCT.