Detection of minimal residual disease in pediatric acute lymphoblastic leukemia

Minimal residual disease (MRD) is a powerful predictor of the overall response to treatment in childhood acute lymphoblastic leukemia (ALL). The most reliable and validated methods to assess MRD in ALL are flow cytometric (FCM) analysis of leukemia-associated immunophenotypes and polymerase chain reaction (PCR) amplification of antigen-receptor gene rearrangements. Results of studies correlating MRD with clinical outcome and technical improvements in FCM technology support the implementation of MRD studies by this method in the clinic. Gene expression profiling of leukemic and normal cells has identified new MRD markers, which can be incorporated to improve the applicability and sensitivity of FCM-based MRD monitoring. The combined use of MRD and emerging information on genetic lesions of ALL offers the possibility of further refining risk-assignment approaches.