Detection of minimal residual disease in acute leukemia by flow cytometry

Patients with acute leukemia in clinical remission may still have up to 10( 10) residual malignant cells (the upper limit of detection by standard morp hologic techniques). Sensitive techniques to detect minimal residual diseas e (MRD) may allow better estimates of the leukemia burden and help the sele ction of appropriate therapeutic strategies. Flow cytometry and polymerase chain reaction have emerged as the most promising methods for detecting sub microspopic levels of leukemia. Flowcytometric detection of MRD is based on the identification of immunophenotypic combinations expressed on leukemic cells hut not on normal hematopoietic cells. It affords the detection of on e leukemic cell among 10,000 normal bone marrow cells, and can be currently applied to at least two thirds of all patients with acute leukemia. Prospe ctive studies in large series of patients have demonstrated a strong correl ation between MRD levels during clinical remission and treatment outcome. T herefore, MRD assays can be reliably used to assess early response to treat ment and predict relapse. In this review, we discuss methodologic aspects a nd clinical results of flowcytometric detection of MRD in patients with acu te leukemia. (C) 1999 Wiley-Liss, Inc.