Pediatric Hematologist/Oncologists' Beliefs about Hematopoietic Stem Cell Transplant for Children with Sickle Cell Disease: A Sickle Cell Transplant Advocacy and Research Alliance (STAR) Study
Authors: Meier Emily Riehm , Abraham Allistair , Ngwube Alexander I. , Janson Isaac , Guilcher Gregory M.T. , Horan John T. , Kasow Kimberly A. 
Published: November 2019

Background
Hematopoietic stem cell transplantation (HSCT) provides a curative therapy for children severely affected by sickle cell disease (SCD). Rejection-free survival following a matched sibling donor (MSD) HSCT for these children is very high. As safer approaches are developed, using reduced intensity conditioning and improved graft versus host disease prophylaxis, there is rationale for extending MSD HSCT to less severely affected children to spare them increasing morbidity and early mortality in adulthood. Providers' perceptions may contribute to the slow adoption of MSD HSCT for less severe SCD. In this study we assess providers' perceptions about MSD HSCT for children with variable SCD severity and determine the influence of provider characteristics on HSCT attitudes.
Methods
Pediatric Hematologists/Oncologists (PHO) were eligible to participate in this IRB exempt study. An e-survey was distributed to all STAR members and ASH members who self-identified as PHO and posted on the American Society of Pediatric Hematology/Oncology Clinical Forum listserv. Analysis was performed to describe participant demographics and the proportion of participants who practice exclusively Pediatric Hematology with a focus on SCD (PSCD) vs. general PHO; we evaluated correlations between these characteristics and likelihood of HSCT referral for each scenario.
Results
Of the 203 respondents, 59% were female, and 69% were between the ages of 30 and 49 years. Spearman's rank correlation analysis did not reveal any significant relationship between respondent age and likelihood to refer to HSCT for any of the survey scenarios. Two-thirds self-identified as Caucasian, 19% Asian, 7% African American and 3% Hispanic. 35% of respondents practiced general PHO, 20% PSCD, 20% Pediatric Hematology, 15% Pediatric HSCT, and 4% Hemostasis.
The majority (75%) of respondents were very or somewhat likely to order HLA typing for a child with HbSS/HbSβ⁰thalassemia who had full siblings, regardless of disease severity. Only 48% would refer a child with HbSS/HbSβ⁰thalassemia who had an HLA-MSD but never admitted to the hospital; referral likelihood differed significantly by practice focus [PHO: 23% very or somewhat likely vs. 54% of PSCD (p=0.002)]. Conversely, 99% of respondents were very or somewhat likely to refer a child who suffered an overt stroke, while 85% and 84% were very or somewhat likely to refer a child who had an abnormal TCD or silent infarct, respectively. 49% of respondents were very or somewhat likely to refer a child with HbSS/HbSβ⁰thalassemia if they had a history of suboptimal adherence to hydroxyurea; referral likelihood again differed by practice focus [PHO: 35% very or somewhat likely vs. 64% PSCD (p=0.021)]. Concern about transplant related mortality (TRM) was the predominant reason for not referring.
For children with severe clinical phenotypes of HbSC and HbSβ+thalassemia, 78% of respondents were very or somewhat likely to refer, compared to only 23% who would refer asymptomatic children with SCD variants. PHO and PSCD did not differ in the likelihood to refer either group. 87% of respondents were very or somewhat likely to refer a child with β-thalassemia major for MSD HSCT, regardless of disease severity; no statistically significant difference was found between PHO and PSCD in referral likelihood. A significantly higher proportion of respondents would refer an asymptomatic child with β-thalassemia major (87%) than those who were very or somewhat likely to refer an asymptomatic child with HbSS/HbSβ⁰thalassemia (47%, p<0.00001) or other SCD variants (23%, p= 0.0005).
Discussion
HSCT is a curative therapy for people with SCD. There was almost complete agreement that a HSCT referral should be made for children with HbSS/HbSβ⁰thalassemia and cerebral vasculopathies who have an MSD, but attitudes varied for almost every other clinical scenario posed. PSCD providers were more likely to refer asymptomatic patients and those with questionable adherence to hydroxyurea compared to general PHOs. TRM was the most common reason for not referring an asymptomatic child for MSD HSCT. Yet, TRM is low in the setting of pediatric MSD HSCT for SCD. Additional education about the decreased quality of life in aging people with SCD and their lack of improvement in life expectancy is needed so that physician perception of HSCT changes and the number of young asymptomatic children with SCD referred for MSD HSCT increases.

Disclosures
Meier: CVS Caremark: Consultancy. Guilcher:Jazz Pharmaceuticals: Other: ASH 2017 meeting attendance.