Real World Utilization of Cranial or Craniospinal Radiation in Adult Acute Lymphoid Leukemia Patients: Data from the Center for International Blood and Marrow Transplant Research

Abstract

Though CNS involvement at diagnosis in adult acute lymphoid leukemia (ALL) is relatively rare (3-7%), >50 % of patients will develop CNS relapse without CNS-directed therapy. Radiation therapy is commonly used as part of stem cell transplant (SCT) conditioning. Historically, a cranial boost was given to reduce risk of CNS relapse. While a CNS boost is not a universal part of prophylaxis, CNS directed RT is used in patients at highest risk for CNS relapse following transplantation, typically those with CNS disease at diagnosis or after induction. There is little data on real world utilization of CNS directed radiation as part of SCT for adult ALL patients. The Center for International Blood and Marrow Transplant Research (CIBMTR) database was queried for adult ALL patients undergoing SCT between 2013 - 2019 who received TBI as part of their regimen where data was available on CNS directed RT. Patient demographics, pre-transplant response to induction, CNS status pre/post-transplant, and overall survival information were collected. Results were stratified by cranial irradiation (CNS-RT), craniospinal irradiation (CSI), or no cranial RT (nCRT). Radiation dose is not collected by the CIBMTR. The data presented here are preliminary and were obtained from the Statistical Center of the Center for International Blood and Marrow Transplant Research. The analysis has not been reviewed or approved by the Advisory or Scientific Committees of the CIBMTR. A total of 1240 patients were identified, of which 59 (5%) received CNS-RT, 2 (0.2%) received CSI, 989 (80%) received nCRT, and 190 (15%) had unknown CNS RT status. Median age was younger in patients receiving CNS-RT (26y, range 19-66y) or CSI (34y, 22-46y) compared to patients receiving nCRT (42y, 18-79y). Patients receiving CNS radiation had more advanced disease at time of transplant (17% requiring 3+ lines of induction before CR vs 50% vs 5%, respectively). 24% of CNS-RT patients and 50% of CSI patients had CNS disease at diagnosis compared to 7% of nCRT patients. 37% of CNS-RT patients and 100% of CSI patients had CNS disease prior to transplant compared to 11% of nCRT patients. Overall survival at 1-5 years was numerically higher with CNS-RT compared to no RT, though 95% confidence intervals overlapped at each follow up point. Data from the CIBMTR on real world utilization of CNS-RT or CSI in adult ALL patients suggest inconsistent practice patterns with 11% of patients without any cranial RT having CNS disease prior to transplant and 57% of CNS-RT patients having no CNS disease prior to transplant. These data offer an interesting analysis of current CNS radiation practice patterns in the past 10 years for adult ALL patients, though interpretation is limited by the retrospective nature of the study and by significant limitations of available data.