Leukemias are cancers of cells that would normally develop into different types of blood cells. There are several types of leukemia, which are classified based on their precursor cell line and whether the leukemia is acute (fast growing) or chronic (slower growing).
Acute myeloid leukemia (AML) is a cancer syndrome that starts in the bone marrow and moves quickly into the blood. AML often develops from hematopoietic precursor cells. These malignant cells exhibit abnormal growth and differentiation and suppress normal bone marrow activity (cancer.org).
AML is the most common form of acute leukemia in adults. The median age at diagnosis is approximately 65 years, and incidence increases with age. In the EU, the incidence rate of AML has been estimated to be between 3-4 cases for every 100,000 adults (Sant, Blood, 2010; Smith, Brit Journal of Cancer, 2011).
Myeloblasts with Auer rods characteristic of AML (Image Credit: Paulo Henrique Orlandi Mourao).
The cause of underlying mutations is unknown for most cases of AML arising in adults, but AML is often associated with environmental factors (chemicals, radiation, tobacco, alkylating chemotherapy, retroviruses), myeloproliferative disorders, and Down syndrome (Sant, Blood, 2010; cancer.org).
Persons with AML may present with varying, sometimes nonspecific symptoms, including fever, weight loss, anemia, easy bruising, abnormal bleeding, or infections. AML is suspected when blood tests show increased circulating blast cells (immature myeloid cells), cytopenia (reduced number of mature blood cells), or if patients present with unexplained metabolic emergencies.
AML is rapidly lethal if left untreated. With intensive treatment, 60-80% of young adults achieve complete remission and one-third are ultimately cured. However, increasing age, general health, and other comorbidities all impact how well patients tolerate chemotherapy and survival rates (Döhner, Blood, 2017).
AML is generally treated with chemotherapy and hematopoietic stem cell transplantation. Treatment typically starts with an induction phase of therapy, during which patients receive a combination of the drugs anthracycline and cytarabine. The goal of the induction phase is to achieve complete remission (the disappearance of detectable leukemia cells). Following induction therapy, patients typically continue to receive cytarabine or another chemotherapy, followed by hematopoietic cell transplantation (Döhner, Blood, 2017).
Treatment may put some patients at increased risk for infections, and chemotherapies are toxic to many organ systems. For some patients, treatment with the intent of complete remission may be inadvisable due to age, disabilities, coexisting medical problems or prior treatment (De Kouchkovsky, Blood Cancer J., 2016). Given these risks, there is a need for more effective treatment strategies to improve patient outcomes.