A Phase II Pilot Trial to Estimate Survival After a Non-total Body Irradiation (TBI) Based Conditioning Regimen in Patients Diagnosed With B-acute Lymphoblastic Leukemia (ALL) Who Are Pre-allogeneic Hematopoietic Cell Transplantation (HCT) Next-generation-sequence (NGS) Minimal Residual Disease (MRD) Negative

This study will evaluate the use of non- TBI (total body irradiation) conditioning for B-ALL patients with low risk of relapse as defined by absence of NGS-MRD (next generation sequencing minimal residual disease) before receiving a hematopoietic cell transplant (HCT). Patients diagnosed with B-ALL who are candidates for HCT will be screened by NGS-MRD on a test of bone marrow done before the HCT. Subjects who are pre-HCT NGS-MRD negative will be eligible to receive a non-TBI conditioning regimen as part of the treatment cohort of the study. Subjects who are pre-HCT NGS-MRD positive will be treated as per treating center standard and will be followed in an observational cohort (HCT center standard of care).