Clinical significance of minimal residual disease in leukemia (Review)

Considerable progress has been made in the treatment of acute and chronic l eukemias. Remission rates are generally high and cure rates of up to 80% ca n be achieved in children with acute lymphoblastic leukemia (ALL). However, in many patients the disease will ultimately recur. In most if not all of these patients, relapse is thought to result from subclinical levels of res idual leukemia, termed minimal residual disease (MRD). Therefore, the study of MRD holds a significant potential to understand the biology of relapse and remission and to design new therapies to improve the cure rate of patie nts. A major goal of these studies is to be able and identify patients at a defined risk of relapse which can lead to risk-adapted therapy approaches. Laboratory assays such as polymerase chain reaction (PCR) and multicolor f low cytometry are sensitive enough to detect one leukemic cell in up to 10( 4)-10(5) normal cells and have become ideal tools to monitor MRD. Especiall y PCR has been used extensively. Although a wealth of data has been generat ed, some questions remain as to the impact of monitoring MRD on clinical ou tcome and are the object of this review.