SUN-065 Bone Health Outcomes in a Large, Diverse Pediatric Cohort Undergoing Hematopoietic Stem Cell Transplant

Abstract Background: Impaired bone mineral density (BMD) is a known complication of hematopoietic stem cell transplantation (HSCT) in adults and may lead to increased fracture risk. Little is known in pediatrics about the risks for impaired BMD and fragility (low trauma) fractures after HSCT. Factors that may influence the risk of bone disease include underlying diagnosis, glucocorticoid exposure, and HSCT complications (e.g. graft versus host disease (GVHD)). Our study aims to describe the incidence of fragility fractures in a large diverse pediatric HSCT population and to identify risk factors of both fracture and impaired BMD. Methods: We reviewed the records of 237 patients (age ≤ 21 years at time of transplant) who underwent HSCT at our institution between January 2015 and March 2018. The primary endpoint was incidence of fragility fractures and the secondary endpoint was assessment of BMD on dual-energy X-ray absorptiometry (DXA). We analyzed DXA results at one-year post-HSCT in 72 out of 206 patients alive at 1 year. Results: There were 25/237 (10.5%) patients with evidence of fragility fracture on x-ray. Of those, 18/25 (72%) were spine fractures. For patients who had fractures, median time to fracture was 5.9 months after BMT. Mortality at one-year was proportionally higher, though not significant (p=0.11) in patients who had at least one fragility fracture (24%; 6/25) compared to patients without fragility fracture (12%; 25/212). Vitamin D status at one-year post transplant was sufficient (>20ng/mL) in 94% (160/171) of patients measured. There was no difference in incidence of fracture between vitamin D sufficient and insufficient patients. The median height-for-age adjusted Z-score (HAZ) for spine BMD at one-year post transplant was 0.13 in all patients. The median HAZ spine BMD Z-score in patients with fragility fracture was -1.64, though data was available for only 5 patients. Conclusions: The incidence of fragility fractures, especially vertebral compression fractures, after pediatric HSCT is striking and is higher than in adult populations. Furthermore, there are likely additional asymptomatic patients with occult fractures not detected in out cohort. Additional analysis will assess the associations between underlying medical diagnosis, GVHD, and chronic glucocorticoid exposure on fragility fracture risk. The high incidence of fragility fractures seen in this study advocates for establishing bone health screening protocols with attention toward spinal imaging in pediatric patients undergoing HSCT.