Relapsed acute lymphoblastic leukemia: Is it crucial to achieve molecular remission prior to transplant?

In patients with acute lymphoblastic leukemia (ALL) the risk of recurrent leukemia influences the choice of treatment between chemotherapy and allogeneic hematopoietic cell transplantation. The evaluation of minimal residual disease (MRD) is now considered to be the greatest progress in risk stratification in regard to leukemia recurrence. Achieving molecular remission at the end of induction therapy after diagnosis or after relapse has influenced treatment choice. Failure to achieve molecular remission is considered "high risk" and allogeneic hematopoietic cell transplantation with a suitable donor, the accepted standard. Nevertheless, published reports support lower relapse and higher survival rates for those in molecular remission at transplantation compared to those in morphological remission. In the setting of relapsed ALL, the availability of targeted therapies offers an opportunity for molecular remission so that transplant recipients have the best possible option of attaining sustained remission upon completion of this treatment.