S115 IMPACT OF MESURABLE RESIDUAL DISEASE POSITIVITY ON OUTCOMES FOLLOWING UNMBILICAL CORD BLOOD TRANSPLANTATION: A STUDY FROM THE ACUTE LEUKEMIA WORKING PARTY OF THE EBMT AND EUROCORD

Abstract

Background:Cord blood transplantation (CBT) has been associated with good transplantation outcomes in acute leukemia patients with mesurable residual disease (MRD) at transplantation (Milano et al., N Engl J Med 375 :944–953, 2016).Aims:In the current retrospective analysis we assessed the impact of MRD positivity on CBT outcomes.Methods:Inclusion criteria were adult patients with acute myeloid (AML) or lymphoblastic (ALL) leukemia, undergoing CBT as first allogeneic hematopoietic cell transplantation from 2002–2017, first or second complete remission (CR) at transplantation, and available MRD status at the time of transplantation.Results:Data from 506 patients were included in the survey. Among them, 317 patients had AML and 189 ALL (including 102 patients with Phi‐pos ALL). Patients received either a single unit (n = 227) or a double CBT (n = 279). MRD positivity was reported in 169 patients (33%) while the remaining 337 patients were MRD negative at CBT. MRD was more frequently detected in ALL than in AML patients (P = 0.02), in patients given single CBT than in those receiving double CBT (P = 0.02), and in those given in vivo T‐cell depletion of the graft (P = 0.006). At 2 years, relapse incidence was 18% in patients with MRD negativity versus 33% in those with MRD positivity at transplantation (P < 0.001). Two‐year leukemia‐free survival (LFS) and overall survival (OS) were 57% and 60%, respectively, in MRD negative patients, versus 38% (P < 0.001) and 48% (P = 0.004), respectively, in those with MRD positivity. There was no statistical interaction between the impact of MRD positivity and disease type (AML versus ALL) nor disease status at transplantation (first versus second CR). In multivariate analyses, MRD positivity was associated with a higher risk of relapse (HR = 1.8, P = 0.003), comparable non‐relapse mortality (P = 0.44), worse LFS (HR = 1.4, P = 0.008) and a trend for worse OS (HR = 1.3, P = 0.065). Other factors associated with relapse incidence included reduced‐intensity conditionng (RIC) (HR = 1.8, P = 0.01) and in vivo T cell depletion (HR = 2.2, P < 0.001). Other factors associated with worse LFS included CR2 at transplantation (HR = 1.3, P = 0.04) as well as in vivo T cell depletion (HR = 1.9, P < 0.001)Summary/Conclusion:In acute leukemia patients undergoing CBT achieving MRD negativity at time of transplantation is associated with a lower risk of relapse translated into better LFS. Novel strategies are in need for those leukemic patients with positive MRD pre‐CBT aiming at achieving MRD negativity and thus improving transplantation results.