Relapse in the central nervous system (CNS relapse) is a serious complication in adult acute lymphoblastic leukemia (ALL). Allogeneic hematopoietic cell transplantation (HCT) is typically offered to patients with high‑risk or relapsed/refractory ALL, but contemporary data on the incidence and determinants of CNS relapse after HCT are limited. The study summarized here is a multicenter retrospective analysis that aimed to describe the incidence of post‑HCT CNS relapse in adults with ALL, identify factors associated with CNS relapse after transplant, and quantify the effect of CNS relapse on overall survival (OS).
This analysis included 636 adult patients with ALL who underwent their first allogeneic HCT between 2011 and 2021 at two centers: Stanford Health Care and University of Washington/Fred Hutchinson Cancer Center. The study design was retrospective and multicenter. The abstract reports the primary endpoints and multivariable associations; additional methodological details (for example, specific conditioning regimens beyond TBI‑based versus non‑TBI, definitions used for CNS involvement, MRD assay platforms, follow‑up duration distribution, and salvage therapies after CNS relapse) are not provided in the abstract and would require the full text for further detail.
In this cohort of 636 patients the cumulative incidence of post‑HCT CNS relapse was low but clinically meaningful. The reported cumulative incidences were:
Figures in the study further distinguish isolated CNS relapse from non‑isolated CNS relapse and display cumulative incidence curves, but detailed numeric breakdowns beyond the 1‑ and 3‑year figures are not provided in the abstract.
Three characteristics were identified as significantly associated with a decreased risk of CNS relapse after allogeneic HCT:
Absence of CNS involvement before HCT. Patients without known CNS disease prior to transplant had lower post‑HCT CNS relapse rates.
Pre‑HCT measurable residual disease (MRD) negativity. Patients who were MRD‑negative before transplant had a decreased risk of subsequent CNS relapse.
Receipt of total body irradiation (TBI)‑based conditioning. Patients who received conditioning regimens that included TBI had lower rates of post‑HCT CNS relapse compared with those who received non‑TBI conditioning.
Figure panels in the full article reportedly show cumulative incidence stratified by these factors (CNS involvement before HCT, pre‑HCT MRD status, and TBI‑based conditioning).
The three protective characteristics above (no pre‑HCT CNS involvement, pre‑HCT MRD negativity, and receipt of TBI‑based conditioning) were combined to define a composite low‑risk group. Membership in this composite low‑risk group was associated with a substantially reduced risk of post‑HCT CNS relapse compared with other patients. The reported effect size for the low‑risk group was:
A figure in the article displays cumulative incidence of CNS relapse for the low‑ versus high‑risk groups.
Post‑HCT CNS relapse had a major adverse impact on survival. The association reported in the study was:
The authors also report that earlier occurrence of CNS relapse after HCT correlated with worse outcomes, and the manuscript includes a Smith‑Zee plot illustrating predicted 1‑year OS probabilities for patients with versus without CNS relapse at 1 year.
The study identifies a definable low‑risk patient subgroup (no pre‑HCT CNS disease, pre‑HCT MRD negativity, and TBI‑based conditioning) with substantially lower risk of post‑HCT CNS relapse. The authors suggest that these findings could inform future research to determine whether CNS‑directed interventions during HCT (for example, additional intrathecal prophylaxis or intensified CNS surveillance) might be safely de‑escalated in patients meeting low‑risk criteria. Conversely, patients lacking these protective features may warrant closer CNS‑directed prevention or surveillance strategies.
The abstract presents the primary incidence figures, key associations, and survival impact but omits several details needed for comprehensive appraisal. Specifically, the abstract does not report:
These items require review of the full text for complete assessment.
In a modern multicenter cohort of 636 adults with ALL undergoing first allogeneic HCT (2011–2021), the 1‑ and 3‑year cumulative incidences of post‑HCT CNS relapse were 3% and 6%, respectively. Absence of CNS disease before transplant, pre‑HCT MRD negativity, and receipt of TBI‑based conditioning were each associated with lower post‑HCT CNS relapse risk and together defined a composite low‑risk group with HR 0.31 for CNS relapse. Post‑HCT CNS relapse was strongly associated with worse overall survival (HR 7.33), particularly when relapse occurred earlier after transplant. The authors recommend further studies to evaluate whether CNS‑directed interventions can be de‑escalated in patients meeting low‑risk criteria; additional methodological and outcome details are available only in the full manuscript.