<p><strong>INTRODUCTION: </strong>Our objectives were to design and validate methods to identify relapse and hematopoietic stem cell transplantation (HSCT) in children with acute lymphoblastic leukemia (ALL) using administrative data representing hospitalizations at US pediatric institutions.</p>

<p><strong>METHODS: </strong>We developed daily billing and ICD-9 code definitions to identify relapses and HSCTs within a cohort of children with newly diagnosed ALL between January 1, 2004, and December 31, 2013, previously assembled from the Pediatric Health Information System (PHIS) database. Chart review for children with ALL at the Children's Hospital of Philadelphia (CHOP) and Texas Children's Hospital (TCH) was performed to establish relapse and HSCT gold standards for sensitivity and positive predictive value (PPV) calculations. We estimated incidences of relapse and HSCT in the PHIS ALL cohort.</p>

<p><strong>RESULTS: </strong>We identified 362 CHOP and 314 TCH ALL patients in PHIS and established true positives by chart review. Sensitivity and PPV for identifying both relapse and HSCT in PHIS were&nbsp;&gt;&nbsp;90% at both hospitals. Five-year relapse incidence in the 10&nbsp;150-patient PHIS cohort was 10.3% (95% CI 9.8%-10.9%) with 7.1% (6.6%-7.6%) of children underwent HSCTs. Patients in higher-risk demographic groups had higher relapse and HSCT rates. Our analysis also identified differences in incidences of relapse and HSCT by race, ethnicity, and insurance status.</p>

<p><strong>CONCLUSIONS: </strong>Administrative data can be used to identify relapse and HSCT accurately in children with ALL whether they occur on- or off-therapy, in contrast with published approaches. This method has wide potential applicability for estimating these incidences in pediatric ALL, including patients not enrolled on clinical trials.</p>

<p>The Children's Oncology Group (COG) develops and implements multi-institutional clinical trials with the primary goal of assessing the efficacy and safety profile of treatment regimens for various pediatric cancers. However, the monetary costs of treatment regimens are not measured. AALL0232 was a COG randomized phase III trial for children with acute lymphoblastic leukemia that found that dexamethasone (DEX) was a more effective glucocorticoid than prednisone (PRED) in patients younger than 10&nbsp;years, but PRED was equally effective and less toxic in older patients. In addition, high-dose methotrexate (HD-MTX) led to better survival than escalating doses of methotrexate (C-MTX). Cost data from the Pediatric Health Information System database were merged with clinical data from the COG AALL0232 trial. Total and component costs were compared between treatment arms and across hospitals. Inpatient costs were higher in the HD-MTX and DEX arms when compared to the C-MTX and PRED arms at the end of therapy. There was no difference in cost between these arms at last follow-up. Considerable variation in total costs existed across centers to deliver the same therapy that was driven by differences in inpatient days and pharmacy costs. The more effective regimens were found to be more expensive during therapy but were ultimately cost-neutral in longer term follow-up. The variations in cost across centers suggest an opportunity to standardize resource utilization for patients receiving similar therapies, which could translate into reduced healthcare expenditures.</p>