Minimal residual disease status predicts outcome of acute myeloid leukaemia patients undergoing T-cell replete haploidentical transplantation. An analysis from the Acute Leukaemia Working Party (ALWP) of the European Society for Blood and Marrow Transplantation (EBMT)

Assessment of minimal residual disease (MRD) is being routinely used to assess response in patients with acute myeloid leukaemia (AML). While it is well established that pre-transplant positive MRD studies predict for relapse in patients transplanted either from matched sibling donors or matched unrelated donors, it is currently unknown whether MRD has comparable prognostic value in haploidentical stem cell transplantation (haplo-SCT). To this end we performed a retrospective analysis using the Acute Leukaemia Working Party/European Society of Blood and Marrow Transplantation multicentre registry. All adult AML patients with known MRD status at transplant who underwent a first T-cell replete haplo-SCT while in remission between 2006 and 2016 were included. Two hundred and sixty-five MRD-negative and 128 MRD-positive patients were assessed. In multivariate analysis, MRD-negative patients experienced lower relapse incidence and better leukaemia-free survival (LFS) compared to MRD-positive patients. Subset analysis for MRD-positive patients revealed that patients with donors positive for cytomegalovirus experienced decreased relapse rates as well as increased survival. A 6-month landmark analysis suggests that the clinical benefit of pre-transplant MRD negativity in terms of relapse, overall survival and LFS is realized at this time point. Pre-transplant MRD status is potentially a pivotal prognosticator of outcome in AML patients undergoing T-cell replete haplo-SCT.