Acute Myeloid Leukemia (AML) is a rapidly progressing cancer that originates in the bone marrow and blood. The disease involves the uncontrolled growth of abnormal, immature white blood cells known as myeloblasts. These cells accumulate in the bone marrow, preventing the production of healthy blood components like red blood cells, normal white blood cells, and platelets. Because AML is fast-growing, it requires immediate and intensive medical intervention following diagnosis.
Why AML Staging Is Different
AML is a cancer of the blood and bone marrow, meaning it is systemic, or widespread, throughout the body from the moment it begins. This characteristic is why AML is not categorized using the standard numerical staging system (Stages I through IV) used for solid tumors. That traditional system measures the size of a localized tumor and how far it has spread to other organs. Since AML is already present in the bloodstream and bone marrow, doctors use the AML subtype and the patient’s response to therapy to determine prognosis and guide treatment.
How AML Is Classified by Subtype
AML is classified by its characteristics, which function similarly to how stages determine treatment for solid tumors. The older French-American-British (FAB) system categorized AML into subtypes M0 through M7 based on the appearance and maturity of the leukemia cells under a microscope. This older system has largely been replaced by a more precise method.
The current standard is the World Health Organization (WHO) classification system. This system incorporates morphology, cell maturity, and specific genetic and molecular markers. The WHO system divides AML into categories based on recurring genetic abnormalities, such as translocations or specific gene mutations like FLT3 or NPM1. Identifying these specific genetic changes is important because they predict how the disease will behave and which treatments are most likely to be effective. For example, AML with favorable genetic markers may respond well to chemotherapy alone, while others with high-risk changes may require a stem cell transplant.
The Three Phases of AML Treatment
While AML is not categorized by stages, the patient’s journey is defined by three distinct phases of treatment designed to manage the disease.
Induction
The first phase is Induction, an intensive chemotherapy regimen aimed at rapidly killing the majority of leukemia cells. The goal is to achieve a complete remission, meaning the bone marrow contains less than five percent myeloblasts, and blood counts have recovered to normal levels.
Consolidation
The second phase is called Consolidation, or post-remission therapy, which begins once remission has been achieved. This phase is less intense than induction but is necessary to eliminate any remaining leukemia cells that may be undetectable. High-dose chemotherapy, often with cytarabine, is commonly used to prevent the disease from relapsing. In many cases, a stem cell transplant is used as the most aggressive form of consolidation.
Maintenance/Monitoring
The final phase is Maintenance/Monitoring, a longer-term strategy that follows consolidation therapy. This phase involves less intensive, sometimes oral, chemotherapy or targeted drug therapy administered over months or years. This is particularly important for patients with a high risk of relapse. For all patients, this phase includes careful monitoring to detect any measurable residual disease (MRD) or signs that the leukemia is beginning to return.