Detection of minimal residual disease in acute and chronic leukemias

The study of minimal residual disease is an attempt to redefine the concept of remission. Opinion as to the clinical utility of minimal residual disease is still in evolution. It has become clear that the ability to merely detect minimal residual disease by the polymerase chain reaction amplification of the molecular "fingerprint" of a leukemia does not always foretell relapse. Rather, careful consideration must be taken of the context of the type of disease, the molecular lesion itself, and the type of therapy employed. Thus although the detection of minimal residual disease in acute lymphoblastic leukemia or acute promyelocytic leukemia has a high correlation with relapse, detection of minimal residual disease in t(8;21) acute myelogenous leukemia has little correlation with relapse. In some diseases (eg. chronic myeloid leukemia) the clinical relevance of minimal residual disease detection may be strengthened by quantification, although this in itself introduces another level of complexity and potential pitfalls. Nevertheless, we are moving toward the day when the molecular definition of disease status will guide therapy.