Isolated Extramedullary Relapse in Acute Lymphoblastic Leukemia: What Can We Do Before and After Transplant?

• Isolated EMR is defined as the presence of clonal blasts in any tissue other than the medullary compartment with a bone marrow evaluation with less than 5% clonal blasts and a full donor chimerism. • Patients with iEMR have shown better survival outcomes when compared to BMR and EMR and in most cases it heralds a systemic relapse. • Risk factors for iEMR include: younger age, history of EMD, poor risk cytogenetics, advanced disease at HSCT, development of GVHD, and non-TBI based conditioning regimens. • Combination therapy, local and systemic, can achieve better remission rates in this subgroup of patients.