Very Young Children Who Undergo Hematopoietic Cell Transplantation at Weight Extremes Have Inferior Overall Survival and Increased Transplant Related Morality

Background Extremes in weight, both underweight and obesity, prior to hematopoietic cell transplantation (HCT) is associated with increased mortality in adults and some groups of children. However, very young children have been excluded in these studies because body mass index (BMI) is not validated in this age group. We aimed to describe the relationship of pre-HCT weight and overall survival and transplant related mortality and to determine if severe weight loss in the immediate post HCT period is associated with increased mortality. Methods In this retrospective study, weight, height/length, and outcomes of children who underwent HCT under the age of 3 years from 2008-2017 were collected at multiple time points. CDC definitions were used to define weight groups, all children not classified as severely underweight or obese were considered normal (Table 1). Kaplan-Meier curves for overall survival (OS) were generated. All deaths not related to relapse were considered transplant related mortality (TRM). Cumulative incidence curves for TRM were generated; comparisons between groups were made using Gray's test. Results Overall, 205 children underwent HCT during the study period. Median age at HCT was 1.08 years (range .13-2.96 yrs), 135 (66%) of children received an allogenic HCT, and 123 (60%) were male. Most frequent transplant indications included immune deficiency/dysregulation (n=74), neuroblastoma (n=48) and leukemia (n=35). Fifteen (7%) were obese and 11 (5%) were severely underweight prior to HCT. Among the three weight groups, there were no significant differences in transplant characteristics including the number who received allogenic HCT, HLA loci match >10/10, or transplant indication. Rates of acute graft versus host disease (aGVHD), infection, chronic GVHD, admission to the intensive care unit (ICU) care, days hospitalized in the first 100 days post HCT, and relapse were not statistically different among weight groups. However, obese and severely underweight children had significantly lower OS compared to normal weight children (p=0.0002) (Figure 1A) and higher TRM (p=0.0029) (Figure 1B). Of patients alive at time of discharge, 25/198 (12.6%) lost greater or equal to 5% of their body weight. There was no difference in OS or TRM in children who lost 5% of body weight and those who did not (p>0.14). Conclusion Children less than 3 years old at weight extremes prior to HCT, particularly obese children, have inferior OS and increased TRM. Larger studies are needed to understand how weight extremes may affect outcomes in HCT in young children.