Advances in the immunological monitoring of childhood acute lymphoblastic leukaemia.

In children with acute lymphoblastic leukaemia (ALL), measurements of minimal residual disease (MRD) during therapy provide crucial information about the response to treatment and the risk of relapse. Flow cytometry is a practical and widely applicable tool for monitoring MRD in patients with ALL. This approach is based on the identification of immunophenotypes expressed by leukaemic cells but not by normal lympho-haematopoietic cells in bone marrow and peripheral blood. These phenotypes can identify one leukaemic cell among 10 000 normal cells and are currently applicable to at least 90% of patients with ALL. A strong correlation between flow cytometric measurements of MRD during clinical remission and treatment outcome has been demonstrated, suggesting that these assays should be incorporated into treatment protocols.