The Impact of Low-Dose Cranial Boost on the Long-Term Outcomes of Adult Patients with High-Risk Acute Lymphoblastic Leukemia Undergoing Total Body Irradiation and Allogeneic Hematopoietic Stem Cell Transplantation

Total body irradiation (TBI) is an integral part of the conditioning regimen for patients with acute lymphoblastic leukemia (ALL) undergoing allogeneic, hematopoietic, cell transplantation (allo-HCT). There are conflicting data in the literature regarding the utility of a cranial irradiation boost in high-risk adult ALL without evidence of preexisting central nervous system (CNS) involvement. This study investigates the posttransplant clinical outcomes of patients with high-risk adult ALL undergoing TBI conditioning for allo-HCT with or without a whole-brain boost, without overt CNS involvement at the time of diagnosis.A retrospective cohort study was conducted using a medical record analysis. We identified 58 patients who were treated between January 1998 and December 2016, and met our preset inclusion criteria of adults (age >18 years old) who carried a pathologically confirmed diagnosis of CNS-negative, high-risk ALL, who underwent hematopoietic stem cell transplantation with TBI conditioning. A multivariate analysis of correlation between patient outcomes and collected categorical variables was assessed with stepwise Cox logistic regression. Survival analyses were assessed using the Kaplan-Meier technique with a log-rank test.With a median follow-up time of 5.3 years, there was a statistically significant improvement in actuarial 7-year CNS relapse-free survival (100% vs 76.4%; P = .043) in favor of patients undergoing a cranial boost. There was no statistically significant improvement in 7-year progression-free survival (78.3% vs 62.5%; P = .076) or overall survival (49.4% vs 43.5%; P = .921) with versus without a cranial boost. On multivariate analysis, the presence of a cranial boost was the only identified variable with an independent relationship to CNS relapse-free survival.Adult patients with high-risk, CNS-negative ALL were found to have a statistically significant improvement in CNS relapse-free survival and a trend toward improved progression-free survival with the inclusion of a cranial boost with TBI pretransplant conditioning. Our data indicate that further investigation into the use of cranial boost in this patient population is warranted.