Long-term thyroid disorders in pediatric survivors of hematopoietic stem cell transplantation after chemotherapy-only conditioning

Background: Thyroid dysfunction (TD) was usually described in hematopoietic stem cell transplantation (HSCT) recipients who were given total body irradiation (TBI) in the conditioning regimen. Because previous studies have reported discrepant results regarding the presence of long-term thyroid complications in HSCT survivors following chemotherapy-only conditioning, we investigated the frequency of thyroid abnormalities in a series of children treated with HSCT for different disorders without TBI as part of the conditioning protocol. Methods: We compared thyroid-stimulating hormone, free thyroxine, total triiodothyronine (TT3), anti-peroxidase (TPO Ab) and anti-thyroglobulin antibodies and thyroid volume z-score in 28 HSCT survivors and 16 healthy subjects matched for age and sex. Results: HSCT recipients had a higher frequency of TD and thyroid complications in total, including TD and euthyroid Hashimoto thyroiditis, compared to the control group. Patients transplanted for Hodgkin lymphoma (HL) were more likely to develop a thyroid complication compared to patients with non-malignant hematologic diseases and leukemia patients. BEAM (carmustine, etoposide, citarabin and melphalan) conditioning compared to busulfan (Bu) and fludarabine (Flu)-based regimens and autologous compared to allogenic grafting were associated with a higher prevalence of TD in our study. HSCT survivors had higher mean serum TT3 levels. A multivariate analysis revealed that autologous (auto)-HSCT recipients had higher mean serum titers of TPO Ab compared to allogenic (allo)-HSCT recipients and controls and the mean thyroid volume z-score was significantly higher in controls compared to auto-/allo-HSCT survivors. Conclusions: We identified a 35.7% prevalence of thyroid abnormalities, emphasizing the need for a long-term surveillance of thyroid function and morphology even in this group of patients who were not exposed to TBI.