Unlike other types of cancer, AML has no staging system.
The way we categorize AML is by different subtypes. The French American, British system (FAB) and World Health Organization (WHO) classification system are two examples of systems used to classify AML into subtypes. Another way we commonly classify AML is by “cytogenetic classification”.
- The FAB classification system divides AML into 7 subtypes: M0, M1, M2, M3, M4, M5, M6 or M7. Discussing the details of this classification system is beyond the scope of this booklet. However, an important subtype worth mentioning is the M3 subtype, which is called “acute promyelocytic leukemia” (or APL for short). This subtype is treated in a different way than all other AML subtypes (M0, M1, M2, M4, M5, M6 and M7). More information on APL treatment is discussed in the “Treatment” section of this booklet.
- Generally speaking, the WHO classification system classifies AML into different subtypes depending on:
- The presence of chromosome abnormalities in leukemia cells (obtained from the cytogenetic evaluation).
- The presence of abnormalities in the appearance of non-leukemia blood-forming cells in the bone marrow (called myelodysplasia).
- Whether AML has occurred because of previous chemotherapy or radiation treatment (therapy-related AML).
Discussion of different WHO AML subtypes is beyond the scope of this booklet.
- Cytogenetic classification is another way used to divide AML into subtypes. This type of classification is based on the absence or presence of chromosome abnormalities (information obtained from cytogenetic analysis, see “Diagnosis” section) AND specific gene mutations found in leukemia cells (information obtained from the molecular evaluation, see “Diagnosis” section).
There are few types of cytogenetic classification systems, a commonly used one being the European LeukemiaNet classification system.
According to this classification system, AML can be grouped in either one of the 4 following subtypes:
- Favorable risk AML.
- Intermediate-risk AML (intermediate I and II).
- Poor or adverse risk AML.
Of note, acute promyelocytic leukemia (APL) is not included in this cytogenetic classification.
Cytogenetic classification helps doctors to:
- Know the prognosis (outlook) of someone with AML, such as the probability of being alive and free of disease five years from the time of diagnosis or the risk of relapse (the risk of leukemia coming back). People with favorable risk AML have the highest chance of being alive over the next 5 years and the lowest chance of relapse after treatment.
In contrast, people with poor or adverse risk AML have the highest chance of relapse after treatment and the lowest chance of being alive over the next 5 years.
For example, one study found that 65% of people with favorable risk AML, 40% of people with intermediate-risk AML and 15% of people with poor-risk AML, respectively, were alive 5 years after being diagnosed with AML.
It is important to keep in mind that these numbers represent averages and do not necessarily predict what will happen to you.
- Decide what is the best treatment for someone with AML (this will be discussed in more details in the next section).