Stephan Grupp, MD, PhD, of the Children’s Hospital of Philadelphia, Philadelphia, PA, discusses the use of molecular detection of measurable residual disease (MRD) to identify relapse in pediatric and young adult B-cell acute lymphoblastic leukemia (ALL) patients treated with tisagenlecleucel. These samples were from patients in the ELIANA (NCT02435849) and ENSIGN (NCT02228096) trials, with samples tested using immunoglobulin next-generation sequencing and flow cytometry. This interview took place at the American Society of Hematology (ASH) 2018 Annual Meeting and Exposition in San Diego, CA.