Induction therapy in the acute leukemias aims to reduce the total body leukemic cell population from approximately 1012 to below the cytologically detectable level of about 109 cells. It is generally assumed, however, that a substantial burden of leukemia cells persists undetected (ie, "minimal residual disease"), leading to relapse within a few weeks or months if no further post-remission therapy (ie, additional consolidation chemotherapy) were administered. However, even when an adult patient is in complete remission (CR) following additional induction and/or consolidation therapy, the majority will ultimately relapse, indicating that attainment of CR, as defined below, is not sufficient to guarantee long-term remission and/or "cure". (See "Induction therapy for acute myeloid leukemia in younger adults".)
This review will discuss the subject of minimal residual disease in patients who have been treated for acute myeloid leukemia (AML) and are in complete remission. Standard morphologic and cytologic methods for diagnosing de novo or relapsed leukemia are discussed separately, although their limitations are briefly reviewed here. (See "Clinical manifestations, pathologic features, and diagnosis of acute myeloid leukemia".)
DEFINITION OF COMPLETE REMISSION (CR)
Complete remission in AML has been defined using the following criteria developed by an International Working Group (table 1) [1-3]:
●Normal values for absolute neutrophil count (>1000/microL) and platelet count (>100,000/microL), and independence from red cell transfusion.
●A bone marrow biopsy that reveals no clusters or collections of blast cells. Extramedullary leukemia (eg, central nervous system or soft tissue involvement) must be absent.