Mixed chimerism (MC) and Minimal Residual Disease (MRD) strongly predict relapse in children with ALL after allo-SCT. Pre-emptive immunotherapy (IT), e.g. withdrawal of immunosuppression (WD-IS) or Donor Lymphocyte Infusion (DLI) can prevent impending relapse. We retrospectively analyzed chimerism and MRD monitoring and the effect of pre-emptive IT.

Results

• Analysis of MRD and chimerism post-transplant are predictive for relapse
  MRD positivity and MC is associated with relapse
  MRD negativity or Complete Chimersism (CC) at one time point does not exclude relapse
• Serial analysis of MRD and chimerism allows for the prediction of relapse in virtually all patients
• Consequence:
  MRD positivity and MC can be efficiently treated by IT
  IT is safe and does not increase risk for treatment-related mortality