Background Donors other than matched siblings and low-intensity conditioning regimens are increasingly used in haematopoietic stem cell transplantation. We aimed to compare the relative risk of donor type and conditioning regimen intensity on the transplantation outcomes of in patients with sickle cell disease. Methods For this retrospective cohort study, we collected data from 90 US centres reported to the Center for International Blood and Marrow Transplant Research. Eligible patients were younger than 50 years, had genetically confirmed sickle cell disease (Hb SS) or sickle beta thalassemia (Hb Sβ), and underwent allogeneic haematopoietic cell transplantation between Jan 15, 2008, and Dec 28, 2017. We considered transplants from donor-recipient pairs matched at the allele-level (HLA-A, HLA-B, HLA-C, and HLA-DRB1), including HLA-matched sibling donors, haploidentical related donors, matched unrelated donors, or mismatched unrelated donors. The main outcome was event-free survival. The effect of donor type, conditioning regimen intensity (myeloablative, non-myeloablative, and reduced-intensity regimens), age (≤12 or 13-49 years), sex, performance score, comorbidity index, recipient cytomegalovirus serostatus, graft type (bone marrow, peripheral blood, or umbilical cord blood), and transplantation period (2008-12 and 2013-17) on outcomes was studied using Cox regression models. Findings Of 996 patients with sickle cell disease and who underwent transplantation in 2008-17, 910 (91%) were included (558 [61%] patients had HLA-matched sibling donors, 137 [15%] haploidentical related donors, 111 [12%] matched unrelated donors, and 104 [11%] mismatched unrelated donors). The median follow-up was 36 months (IQR 18-60) after transplantation from HLA-matched siblings, 25 months (12-48) after transplantation from haploidentical related donors, 37 months (23-60) after transplantation from HLA-matched unrelated donors, and 47 months (24-72) after transplantation from mismatched unrelated donors. Event-free survival was worse in recipients aged 13 years or older than in those younger than 13 years (hazard ratio 1•74, 95% CI 1•24-2•45; p=0•0014) and in those who received a transplant from haploidentical related donors (5•30, 3•17-8•86; p<0•0001), matched unrelated donors (3•71, 2•39-5•75; p<0•0001), and mismatched unrelated donors (4•34, 2•58-7•32; p<0•0001) than in patients who received a transplant from matched siblings. There was no significant difference in event-free survival between recipients of transplants from non-sibling donors: haploidentical related donors (1•43, 0•81-2•50; p=0•21) or mismatched unrelated donors (1•17, 0•67-2•05; p=0•58) versus HLA-matched unrelated donors, or mismatched unrelated donors versus haploidentical related donors (1•22, 0•65-2•27; p=0•98). Event-free survival was also worse in patients conditioned with reduced-intensity regimens (1•97, 1•15-3•36; p=0•013) than in those conditioned with non-myeloablative regimens, but did not differ between those who received myeloablative compared with n...

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Optimal post-remission therapy for adolescents and young adults (AYAs) with Ph-negative acute lymphoblastic leukemia (ALL) in first complete remission (CR1) is not established. We compared overall survival (OS), disease-free survival (DFS), relapse, and non-relapse mortality (NRM) for patients receiving post-remission therapy on CALGB 10403 to a cohort undergoing myeloablative (MA) allogeneic hematopoietic cell transplantation (HCT) in CR1. In univariate analysis, OS was superior with chemotherapy compared to MA allogeneic HCT (3-year OS 77% vs. 53%, P < 0.001). In multivariate analysis, allogeneic HCT showed inferior OS (HR 2.00, 95% CI 1.5–2.66, P < 0.001), inferior DFS (HR 1.62, 95% CI 1.25–2.12, P < 0.001), and increased NRM (HR 5.41, 95% CI 3.23–9.06, P < 0.001) compared to chemotherapy. A higher 5-year relapse incidence was seen with chemotherapy compared to allogeneic HCT (34% vs. 23%, P = 0.011). Obesity was independently associated with inferior OS (HR 2.17, 95% CI 1.63–2.89, P < 0.001), inferior DFS (HR 1.97, 95% CI 1.51–2.57, P < 0.001), increased relapse (1.84, 95% CI 1.31–2.59, P < 0.001), and increased NRM (HR 2.10, 95% CI 1.37–3.23, P < 0.001). For AYA ALL patients in CR1, post-remission therapy with pediatric-style chemotherapy is superior to MA allogeneic HCT for OS, DFS, and NRM.

High-dose busulfan (BU) followed by high-dose cyclophosphamide (CY) before allogeneic hematopoietic cell transplantation (HCT) has long been used as treatment for hematologic malignancies. Administration of phenytoin or newer alternative antiepileptic medications (AEMs) prevents seizures caused by BU. Phenytoin induces enzymes that increase exposure to active CY metabolites in vivo, whereas alternative AEMs do not have this effect. Lower exposure to active CY metabolites with the use of alternative AEMs could decrease the risk of toxicity but might increase the risk of recurrent malignancy after HCT. Previous studies have not determined whether outcomes with alternative AEMs differ from those with phenytoin in patients treated with BU/CY before allogeneic HCT. We studied a cohort of 2155 patients, including 1460 treated with phenytoin and 695 treated with alternative AEMs, who received BU/CY before allogeneic HCT between 2004 and 2014. We found no differences suggesting decreased overall survival or relapse-free survival or increased risks of relapse, nonrelapse mortality, acute or chronic graft-versus-host disease, or regimen-related toxicity associated with the use of alternative AEMs compared with phenytoin. The risk of dialysis was lower in the alternative AEM group than in the phenytoin group. Alternative AEMs are safe for prevention of seizures after BU administration and can avoid the undesirable toxicities and drug interactions caused by phenytoin.

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