Allogeneic Hematopoietic Stem Cell Transplantation in Children and Adults with Chronic Granulomatous Disease (CGD): A Study of the Inborn Errors Working Party (IEWP) of the EBMT

Introduction: Chronic granulomatous disease (CGD) is a rare primary immunodeficiency disease characterized by impairment of the phagocyte NADPH-oxidase complex, resulting in deficient microbial killing and life-threatening bacterial and fungal infections. Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is the only curative approach, but it can be complicated by graft failure, graft versus-host disease (GvHD) and transplant-related mortality (TRM). In order to define prognostic risk factors in this setting, the IEWP of the EBMT performed a large retrospective registry study on 600 pediatric and adult patients with CGD undergoing allo-HSCT.

Patients and Methods: We analyzed the outcome of patients with CGD who received allo-HSCT in EBMT centers between 1993 and 2017. The main end-points of the study were overall survival (OS) and event-free survival (EFS; events were death and primary or secondary engraftment failure) according to patient's age, donor type, stem cell source and conditioning regimen. One patient died before allo-HSCT and was excluded from analysis.

Results: We studied 536 children (aged < 18 years) and 63 adults (aged ≥ 18 years) affected by CGD. The median follow-up was 45.37 months (IQR 15.8-81.8). Genetic results were available for 307 patients: inheritance was X-linked (75%) or autosomal recessive (25%). Median age at transplant was 7.2 years (range: 0.12-48.56). Conditioning regimen was Busulfan/Fludarabine (n=244; 41%), Busulfan/Cyclophosphamide (n=104; 17%), Treosulfan/Fludarabine (n=76; 13%), Treosulfan/Fludarabine/Thiotepa (n=52; 9%) or other drug combinations (n=123; 20%). Donors were human leukocyte antigen (HLA) matched related (MFD, 10/10; n=211, 40%), matched unrelated (MUD, 10/10 or 6/6 in UCB; n=201; 38%), mismatched related (MMFD, ≥ 9/10; n= 27; 5%) or mismatched unrelated (MMUD, ≥ 9/10 or 5/6 in UCB; n= 83; 16%). Stem cell source was bone marrow (BM; n=408; 69%), peripheral blood (PB; n=153; 26%) or umbilical cord blood (UCB; n=27; 5%). Donor engraftment occurred in 516 evaluable patients (88%), while primary or secondary engraftment failure occurred in 68 patients (12%). Seventy-nine patients (13%) died after allo-HSCT.

The 2 year Kaplan-Meier estimate of OS and EFS were 87.1% (95% CI, 84.2-89.9) and 77.8% (95% CI, 74.2-81.4), respectively (Fig A). The 2-year cumulative incidence of grade II-IV acute GvHD, chronic GvHD and extensive chronic GvHD was 18.6% (95%, 15.1-22.2), 16.2 % (95%, 18.8-19.7) and 5.5% (95%, 3.4-7.7), respectively. A univariate cox model with spline term demonstrated that older age at transplant was associated with an increased risk of death (p=0.002). Children undergoing allo-HSCT had a superior 2y OS (88.1%; 95% CI 85.2-91.0), compared to adults (78.2%; 95% CI, 67.7-88.7), p=0.03 (Fig B). Patients undergoing allo-HSCT from a MFD had a superior EFS (86.5%; 95% CI 81.5-91.4) compared to MUD (73.3%; 95% CI 66.7-79.9), MMUD (78.2%; 95% CI 69-87.5) and MMFD (59.7; 95% CI 40.4-79.1), p< 0.001 (Fig C). Patients receiving BM grafts had superior 2y EFS (81.0%; 95% CI 76.9-85.1) compared to PB (72.5%; 95% CI 64.7-80.4) and UCB (66.7%; 95% CI 48.9-84.4), p=0.04. The pattern of disease inheritance and the choice of conditioning regimen didn't have an impact on outcome (Fig D). Fifty-three patients with graft failure underwent a second allo-HSCT and the 2y OS in this group was 82.1% (95% CI, 71.5-92.7). Year of transplantation didn't have an influence on outcome.

Conclusion: This is the largest study describing the outcome of allo-HSCT in children and adults affected by CGD. We demonstrate an excellent outcome, with a low incidence of graft failure, TRM and GvHD. Older patients with CGD have reduced survival after allo-HSCT, indicating that transplant should be considered at a younger age. The use of a MMFD is associated with poorer outcome; indication to transplant in this setting should be carefully evaluated by the treating physicians.

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