A Multicenter Retrospective Analysis Stressing the Importance of Long-Term Follow-Up after Hematopoietic Cell Transplantation for β-Thalassemia

Allogeneic hematopoietic cell transplantation (HCT) is curative in patients with beta-thalassemia major. However, most reports on HCT outcomes lack long-term follow-up data with the exception of single-center reports. An international multicenter retrospective data collection and analysis was conducted in 176 beta-thalassemia patients who were 1 year or beyond after first HCT to evaluate follow-up methods and outcomes at 7 centers. Median age at HCT was 5.5 years (range,.6 to 18.5), and median follow-up was 7 years (range, 1 to 20). HCT was predominantly from HLA-matched related donors (91%) with bone marrow as stem cell source (91%) and myeloablative conditioning regimens (88%). Late mortality or persistent chronic graft-versus-host disease (GVHD) was rare (<2%). Graft rejection was reported in 23% (24% of these occurred beyond 1 year) post-HCT. Of 119 patients with donor chimerism results available for >= 4 years post-HCT, 50% had >95%, 22% had 50% to 95%, 7% had 20% to 50% and 25 (21%) had <20% donor chimerism. Organ dysfunction was identified in 10% pre HCT and in 20% post-HCT even without complete clinical details on all patients. Hypogonadism and elevated creatinine for age were most commonly reported and significantly higher in recipients >= 7 years at the time of HCT (P =.007) and in those with pre-existing morbidity before HCT (P =.02). Outcomes were unaffected by pre-HCT ferritin or GVHD. Mean z scores for height and weight were low at baseline and remained low post-HCT (79%), confirming that growth impairment from disease lacked recovery post-HCT during this followup period. HCT for beta-thalassemia has a high rate of cure and low mortality, especially in the young and from HLA-matched related donors. Half of the number of recipients live with mixed chimerism that requires continued follow-up because of a risk of late graft rejection (14%). Organ function after HCT when <7 years of age was generally preserved. Hypogonadism, renal dysfunction, and growth impairment that failed to correct were late complications identified most frequently in older transplant recipients. Systematic follow-up of individual organs such as lung and heart were inadequate but important. These data support the development of simple measures of uniformly tracking long-term HCT outcomes and organ functions in children and adolescents who undergo HCT for thalassemia, allowing for systematic identification and implementation of standardized surveillance strategies and interventions. (C) 2017 American Society for Blood and Marrow Transplantation.