Acute Myeloid Leukemia (AML) is a fast-growing cancer that originates in the bone marrow, where blood cells are made. This disease involves the rapid production of abnormal white blood cells, called blasts, which interfere with the bone marrow’s ability to produce healthy blood cells. For individuals diagnosed with AML, achieving remission is the primary objective of initial treatment. Remission indicates a temporary absence of detectable leukemia cells in the body.
Defining Remission in AML
Complete remission (CR) in AML signifies specific clinical criteria are met following treatment. This includes the restoration of normal peripheral blood cell counts, meaning healthy levels of neutrophils, platelets, and red blood cells are present. A bone marrow biopsy must show less than 5% blast cells. Individuals in complete remission should also be free of any signs or symptoms of leukemia.
Confirming remission involves tests, with a complete blood count (CBC) to check blood cell levels. A bone marrow aspiration and biopsy is then performed to microscopically examine the bone marrow and determine the percentage of blast cells. Even after achieving complete remission, a small number of leukemia cells, undetectable by standard tests, can remain; this is termed Minimal Residual Disease (MRD).
More sensitive laboratory techniques, such as multiparameter flow cytometry or polymerase chain reaction (PCR) tests, are used to detect MRD. Flow cytometry identifies specific markers on the surface of leukemia cells, while PCR detects specific genetic mutations unique to the cancer. An MRD-negative status, meaning no remaining leukemia cells are found by these highly sensitive tests, is a more favorable outcome, often associated with a lower chance of the disease returning.
The Path to Initial Remission
The initial phase of treatment for AML, known as induction therapy, is designed to achieve complete remission by destroying the majority of leukemia cells. A common approach involves a combination of chemotherapy drugs, often referred to as the “7+3” regimen. This typically includes seven consecutive days of continuous infusion of cytarabine, a drug that interferes with DNA synthesis in cancer cells, combined with three days of an anthracycline drug, such as daunorubicin or idarubicin, which damages cancer cell DNA.
This intensive chemotherapy often requires a hospital stay, typically lasting several weeks, as patients experience significant side effects. The medications not only target leukemia cells but also affect rapidly dividing healthy cells, leading to a period of very low blood counts. This can result in increased susceptibility to infections, requiring close monitoring and supportive care, including antibiotics and blood transfusions. The purpose of this phase is to allow healthy blood cell production to recover.
Maintaining Remission
After achieving initial remission, the next phase, known as post-remission or consolidation therapy, aims to eliminate any remaining leukemia cells that might have survived induction therapy, including any undetectable Minimal Residual Disease (MRD) cells. The choice of consolidation therapy depends on various factors, including the patient’s age, overall health, and the specific genetic characteristics of their AML.
One common approach is consolidation chemotherapy, which involves several additional cycles of chemotherapy, often using high-dose cytarabine (HiDAC). These cycles are administered to further reduce the chance of relapse by targeting residual leukemia cells. HiDAC specifically uses higher concentrations of cytarabine than in induction.
For some patients, particularly those with higher-risk AML or specific genetic mutations, an allogeneic stem cell transplant may be recommended. This intensive procedure involves replacing the patient’s bone marrow with healthy blood-forming stem cells from a matched donor. Before the transplant, the patient undergoes high-dose chemotherapy and sometimes radiation to eliminate their own bone marrow and any remaining leukemia cells. The transplanted donor cells then engraft and begin producing healthy blood cells, by introducing a new immune system that can recognize and destroy leukemia cells.
Newer treatment approaches also include targeted therapies or maintenance therapies, which may be used after initial treatment to help sustain remission. These drugs specifically target certain genetic mutations or pathways within leukemia cells. The decision regarding which consolidation or maintenance strategy to pursue is individualized, based on the patient’s disease characteristics and their ability to tolerate intensive treatments.
The Risk of Relapse
Despite achieving remission, the risk of AML returning, known as relapse, remains. Relapse occurs when leukemia cells that survived initial and consolidation therapies begin to proliferate again. These cells may have been undetectable by standard tests, existing as Minimal Residual Disease (MRD).
Several factors influence the likelihood of relapse. The specific subtype of AML and the presence of certain genetic mutations or chromosomal abnormalities at diagnosis can indicate a higher risk. For instance, some genetic profiles are associated with more aggressive disease. The presence of Minimal Residual Disease (MRD) after induction or consolidation therapy is another strong predictor of relapse; an MRD-positive status suggests a higher burden of residual leukemia cells.
To monitor for any signs of relapse, regular follow-up appointments are a routine part of post-remission care. These typically involve periodic blood tests, such as complete blood counts, to check for any abnormalities in blood cell levels. In some cases, repeat bone marrow examinations may also be performed to microscopically assess the bone marrow for the return of blast cells. This ongoing surveillance allows for early detection.