Effectiveness of prophylactic intrathecal chemotherapy and risk factors of central nervous system relapse after allogeneic hematopoietic cell transplantation in acute myeloid leukemia

Central nervous system (CNS) relapse in acute myeloid leukemia (AML) is uncommon but associated with poor outcomes. This retrospective study analyzed 960 AML patients who underwent hematopoietic cell transplantation (HCT) at Asan Medical Center between 2000 and 2020 to assess the efficacy of prophylactic intrathecal chemotherapy. Per protocol, patients received up to four intrathecal methotrexate (MTX). CNS relapse occurred in 2.8%, with a median onset of 6.3 months post-HCT. The 5-year CNS relapse rate was lower in the prophylactic MTX group compared to the non-MTX group (2.7% vs. 7.4%, p = 0.132), though not statistically significant. Increased number of intrathecal treatments did not reduce CNS relapse. Risk factors for CNS relapse included high white blood cell count, extramedullary disease, FAB M3/M4, and poor-risk cytogenetics. Prior CNS involvement was significant only in univariate analysis. These findings suggest intrathecal prophylaxis may benefit high-risk patients but is not necessary for all AML patients undergoing HCT.