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Introduction. Limited data exist regarding the role of haploidentical HCT (haplo-HCT) in hemoglobinopathies, whereas long-term outcomes and late effects among these patients are largely unknown. We compared long-term outcomes in two groups of patients underwent halpo-HCT using different in vitro depletion strategies.
Methods. Fifty four consecutive patients, aged <17 years, received a haploidentical (≥2 HLA-mismatched antigens) transplant for thalassemia (n=45) or sickle cell disease-SCD (Hb SS, n=7 and HbS/beta thalassemia, n=2). Among these patients 32 received CD34+ selected PBSC and bone marrow grafts, and 8 patients received CD34+ selected PBSC and CD3+/CD19+ depleted bone marrow grafts between December 2005 and December 2011(group A), whereas 14 patients received TCRαβ+/CD19+ depleted PBSC grafts between June 2012 and March 2017 (group B). The conditioning regimen consisted of oral/weight-based IV BU, Thiotepa (10 mg/kg/d), CY (200 mg/kg) and rabbit ATG preceded by preconditioning with hydroxyurea (30 mg/kg/d), azathioprine (3 mg/kg/d) from D −59, and fludarabine (30-35 mg/m2/d) from D −16 through D −11. Short-course CSA/methylprednisolone or CSA/MMF was given as GVHD prophylaxis until D+60. Eighty and 85% of patients received hematopoietic cells from mother in group A and group B, respectively. The two groups showed similar patient demographics.
Results. The median follow-up among surviving patients was 90 months (range, 68-139) for group A and 46 months (range, 5-62) for group B. Median CD34+ cell dose in group A and B was 16x106/kg (range, 4.3-28.1) and 15.7 x106/kg (range, 8.1-39.2) (P=0.43), respectively. The grafts of group A patients contained median of 2.8 x105/kg CD3+ and 0.21x106/kg CD19+ cells. The grafts of group B patients contained median of 4x104/kg (range, 1-10.0) αβ T cells, 9x106/kg (range, 2.8-40.2) γδ T cells, 0.06x106/kg (range, 0.01-1.7) CD19+ cells, and 28.67x106/kg (range, 9.8-194.3) CD16+/56+ cells. Sustained engraftment occurred in 55% versus 86% in group A and B (P=0.05), respectively. Group B patients showed significantly faster platelet and neutrophil recovery. Graft failure (GF) occurred in 18 group A (primary GF in 12 and secondary GF in 6 patients) and one patient each in group B had PGF and SGF. The incidence of GF was significantly higher among patients of group A (45%) than of group B (14%) (P= 0.048). Respective OS and DFS were 78% versus 84% (P=0.9), and 39% versus 69% (P=0.085) (Figure 1). The incidence of grade 2-4 aGVHD in groups A and B were 29% and 28%, respectively. Three patients in group A and one in group B developed grade 3-4 acute GVHD with visceral involvement. The remaining patients in both groups had grade 2 acute skin GVHD. The incidence of moderate chronic GVHD was 10% and 21% in group A and B (P= 0.1), respectively. Both groups showed similar CD3+, CD4+, CD8+, CD19+ and CD56+ immune reconstitution with suboptimal CD4+ recovery within the first year: absolute (mean±SEM) cells/ul of CD4+ in group A and B at D+180 were 148±43 and 169±36, respectively (P=0.64). Respective one year absolute cells/ul of CD3+, CD4+, CD8+, CD19+ and CD56+ were 1014±238, 423±97, 559±147, 600±241, 413±151 vs 832±250, 295±74, 415±140, 307±103, 182±49. In group A, 8 patients died due to pneumonia (D+29), perianal abscess (D+33), CMV pneumonia (D+190 ), diffuse large B-cell lymphoma (DLBCL) (D+199), disseminated aspergillosis (D+243), toxic megacolon (+1.2 years), acute heart failure (+ 4 years) and overwhelming postsplenectomy sepsis (+7.4 years). In group B 2 patients died from gastrointestinal bleeding (D+222) or DLBCL (+1.7 years).
The frequency of complications were similar in both groups. The incidence of EBV reactivation/PTLD was significantly higher in patients who did not receive prophylactic rituximab (26%) than who did (4%) (P=0.03).
Conclusions. This study showed that the use of TCRαβ+/CD19+ depleted grafts was associated with a reduced rate of GF and improved DFS compared with CD34+selected/CD3+CD19+- depleted grafts in hemoglobinopathies. However, delayed immune reconstitution and infectious complications remain major causes of morbidity and mortality in these patients. Additional strategies to improve immune recovery are needed.
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