Vitamin D Deficiency in Pediatric Hematopoietic Stem Cell Transplantation Patients Despite Both Standard and Aggressive Supplementation.

We recently reported that more than 70% of pediatric and young adult patients had a vitamin D (VD) deficiency at the time of their hematopoietic stem cell transplantation (HSCT). Moreover, VD deficiency was associated with inferior survival at 100 days after transplantation. The goal of the present study was to evaluate the VD requirements needed to maintain an optimal VD level (30 to 60 ng/mL) during the first 3 months after transplantation using real-time VD monitoring and personalized VD supplementation. We examined 2 cohorts in this study: cohort 1, the "preintervention" cohort (n = 35), who were treated according to National Kidney Foundation guidelines for VD therapy, and cohort 2, the "intervention" cohort (n = 25) who were treated with high-dose VD with an aggressive dosage increase in those who remained VD-insufficient. Results from cohort 1 showed that despite aggressive monitoring and VD supplementation, therapeutic vitamin D levels were difficult to achieve and maintain in HSCT recipients during the early post-transplantation period. Only 43% of cohort 1 achieved a therapeutic VD level, leading to our intervention in cohort 2. Outcomes improved in cohort 2, but still only 64% of cohort 2 patients achieved a therapeutic VD level despite receiving >200 IU/kg/day of VD enterally. The median VD level in patients who did achieve sufficient levels was 40 ng/mL, with only 1 patient in each cohort achieving a supratherapeutic but nontoxic level. These data indicate that standard guidelines for VD replacement are inadequate in HSCT recipients, and further work is needed to define more appropriate dosing in this clinical setting.