Remission Criteria

The first goal in the treatment of AML is to eradicate all identifiable evidence of leukemia, also known as complete remission (CR).

CR has traditionally been defined in the United States using morphological criteria such as the following:

Alternative definitions of remission using morphology are used in AML because of the prolonged myelosuppression caused by intensive chemotherapy. These definitions include CR with incomplete platelet recovery (CRp) and CR with incomplete marrow recovery (typically absolute neutrophil count) (CRi). Whereas the use of CRp provides a clinically meaningful response in studies of adults with AML, the traditional CR definition remains the gold standard because patients in CR were more likely to survive longer than those in CRp.[8]

Achieving a hypoplastic bone marrow (using morphology) is usually the first step in obtaining remission in AML, with the exception of the M3 subtype (acute promyelocytic leukemia [APL]). In APL, a hypoplastic marrow phase is often not necessary before the achievement of remission. Additionally, early recovery marrows in any of the subtypes of AML may be difficult to distinguish from persistent leukemia, although the application of flow cytometric immunophenotyping and cytogenetic/molecular testing have made this less problematic. Correlation with blood cell counts and clinical status is imperative in passing final judgment on the results of early bone marrow findings in AML.[9] If the findings are in doubt, a bone marrow aspirate should be repeated in 1 to 2 weeks.[2]

In addition to morphology, more precise methodology (e.g., multiparameter flow cytometry or quantitative reverse transcriptase–polymerase chain reaction [RT-PCR]) is used to assess response. These methods have proven to be of greater prognostic significance than morphology. For more information about these methodologies, see the Prognosis and Prognostic Factors section.