Leukemia is a general term used to describe cancers of the blood caused by abnormal production of blood cells in the bone marrow. The bone marrow is the spongy tissue inside of the bones that produces the different types of blood cells. The three major types of blood cells are white blood cells, red blood cells and platelets. There are two types of white blood cells: myeloid cells, which help directly fight infection, and lymphoid cells, which make up the immune system. Red blood cells carry oxygen to the body’s tissue. Platelets help prevent bleeding. In a healthy bone marrow, there are cells called “blasts”, which are immature cells that develop into normal blood cells. Acute Myeloid Leukemia (AML) occurs when there is a rapid overproduction of immature white blood cells called myeloblasts. This causes a “crowding out” effect on the remainder of the bone marrow, resulting in decreased production of normal blood cells. This can lead to anemia, bleeding, and impairment of the immune system. AML is the most common acute leukemia in adults occurring in approximately 3 to 5 out of every 100,000 people in the United States. The average age at diagnosis is 65 years old. AML is more common in men than in women.
Most patients have symptoms due to the lack of normal blood cells and excess of leukemia cells in the body. Signs and symptoms can include fevers, recurrent infections, fatigue, weakness, shortness of breath, pale skin, easy bruising, nosebleeds, gum bleeding, tiny red spots under the skin or in the mouth (called petechiae), bone pain, , and occasionally confusion or disorientation.
Risk Factors for Developing Acute Myeloid Leukemia
Most patients with AML do not have any known risk factors for the disease. However, several risk factors are associated with an increased risk of developing AML. Environmental risk factors include certain types of chemotherapy, radiation therapy, tobacco smoke, and exposure to large amounts of a chemical called benzene. There are several genetic conditions that carry an increased risk of developing AML, including Down syndrome, Fanconi Anemia, and Bloom syndrome. Several blood disorders from which AML can develop include Paroxysmal Nocturnal Hemoglobinuria, Myelodysplastic syndrome and the myeloproliferative neoplasms.
How Acute Myeloid Leukemia is Diagnosed
A preliminary diagnosis of AML can often be made by simple microscopic examination of a blood sample. In patients who have symptoms concerning for leukemia, a complete blood count (CBC) can show either a high or low white blood cell count, low red blood cell count (anemia), and low platelet count. The hallmark of AML on CBC is the presence of myeloblasts. To make a final diagnosis, a bone marrow biopsy and aspirate is performed. Special studies are done on the bone marrow tissue to confirm the presence of myeloblasts. Further studies are then performed to determine if there are any abnormalities of the chromosomes in the leukemia cells. Certain abnormalities are associated with different subtypes of AML and influence treatment options and prognosis. Based on the chromosome findings, patients are categorized into low, intermediate, or high-risk categories.
Treatment Options at Tufts Medical Center
The purpose of receiving treatment is to improve symptoms, increase the chance of cure or prolong survival. Different types of treatments are available. Once diagnosed with AML, the decision regarding which regimen is right for an individual patient should be made under the guidance of a leukemia specialist.
The treatment of AML is divided into two phases: remission induction therapy and post remission (consolidation) therapy.
Phase 1: Remission Induction Therapy
The first phase is remission induction therapy. The purpose of induction therapy is to eliminate the leukemia cells in the blood, bone marrow and tissues. Induction therapy is given soon after the diagnosis is made, often while the patient remains in the hospital.
For patients who can tolerate high doses of chemotherapy, remission induction therapy consists of a combination of chemotherapy medications given over 7 days A standard regimen includes two medications, cytarabine and either daunorubicin or idarubicin. Cytarabine is given as a continuous infusion over seven days. Daunorubicin or idarubicin is given as a once daily infusion on the first three days of treatment. Sometimes this regimen is called “7 + 3” or “seven and three”. It typically takes 2-3 weeks after the chemotherapy is given for the bone marrow to start producing normal blood cells. A bone marrow biopsy and aspirate is repeated to determine if remission has been achieved. If persistent leukemia is seen, another course of induction chemotherapy is given.
The goal of this first phase of treatment is a remission, where the blood counts are normal and there is no visible leukemia in the blood or marrow. However, achieving a remission does not mean the leukemia is cured, and additional therapy is nearly always needed.
Remission induction therapy for patients with a subtype of AML called acute promyelocytic leukemia (PML) includes an oral medication called all-trans retinoic acid (ATRA/Tretinoin). in addition to a short course of intravenous chemotherapy. Some patients may also receive treatment with Arsenic trioxide.
Phase 2: Post-Remission Therapy
After remission is achieved, patients begin post-remission (consolidation) therapy. The goal of this phase is to rid the body of any remaining leukemia cells that cannot be detected under the microscope.
There are two main options for consolidation therapy: more chemotherapy or bone marrow/stem cell transplantation. Transplantation is a complex process during which a patient’s diseased bone marrow is eradicated and replaced by a by healthy stem cells or bone marrow.
In the case of patients in whom high dose chemotherapy or transplantation are not possible, other options for treatments are available. For some patients, participating in a clinical trial (research study) might be the best treatment.
Most new treatments are developed through clinical trials. Your doctor will discuss options with you. All of the above treatments are available through our experts here at Tufts Medical Center.