Physicians devise a course of treatment for each AML patient that takes a number of factors into consideration: the AML subtype; whether the patient has been treated already, and if so with what therapies and how successfully; the number of leukemic cells detectable in the blood; whether any chromosomal alterations have been found; and the patient’s age and overall health. For this reason, AML patients with the same subtype may receive different treatments.
The standard treatment approaches for adult leukemia are chemotherapy, immunotherapy, and hematopoietic stem cell (or bone marrow) transplantation. Radiation therapy — treatment with high-energy rays that destroy cancer cells — is sometimes used for leukemia in the central nervous system or elsewhere and can be included as part of the treatment in preparation for stem cell transplant.
Treatment for AML is typically divided into two phases:
The goal of the remission induction phase is to induce a remission, a state in which there is no visible evidence of disease and blood counts are normal. Patients may receive a combination of drugs during this phase including daunorubicin, idarubicin, or mitoxantrone plus cytarabine.
In the post-remission therapy phase, patients may receive additional treatment to eliminate any remaining leukemic cells. Treatment may consist of cytarabine given alone, often in higher doses, or a combination of drugs such as cytarabine, daunorubicin, idarubicin, mitoxantrone, and etoposide. Some AML patients may undergo either an autologous transplant (using the patient’s own stem cells) or an allogeneic transplant (using stem or bone marrow cells from someone other than the patient) during this phase of treatment.
Treatment for Acute Promyelocytic Leukemia (APL)
Following recent studies of specific agents in patients with the form of AML called acute promyelocytic leukemia (APL), physicians have established treatment guidelines that differ from those for other forms of AML. Most APL patients are now treated initially with all-trans-retinoic acid (ATRA), the use of which was pioneered at Memorial Sloan Kettering, in combination with chemotherapy.(1) ATRA induces a complete response in 80 to 90 percent of patients and has been shown to extend survival.
Treatment with arsenic trioxide, another agent used first at Memorial Sloan Kettering, has been shown to produce remissions in the small percentage of patients who relapse. More recently, its use as consolidation therapy (a type of high-dose chemotherapy often given as the second phase of a cancer treatment regimen) in first remission has been shown to decrease the chance of relapse and improve survival in APL patients.
Following consolidation treatment with arsenic trioxide, APL patients are then given several courses of consolidation chemotherapy, which is likely to include either idarubicin or daunorubicin alone or in combination with cytarabine and ATRA. Doctors then give additional treatment with ATRA to maintain patients’ remissions.
Physicians may include immunotherapeutic drugs throughout the course of treatment. These agents are designed stimulate the patient’s own immune system to recognize and attack the leukemic cells. Monoclonal antibodies may be able to destroy diseased cells directly, or they may be used in a “conjugated” form, with radioisotopes (radioactive substances that irradiate tumor cells), drugs, or toxins designed to attach to tumor cells and destroy them. Gemtuzumab ozogamicin (Mylotarg®) is an example of targeted chemotherapy. It consists of a monoclonal antibody that targets CD33, a protein found on the surface of AML cells, which is linked to a potent antitumor antibiotic known as calicheamicin. This drug is sometimes used for patients with AML who are 60 years or older and whose disease has relapsed, or for whom no other chemotherapy option is possible.
Treatment for CNS Involvement
In rare cases, AML can spread to the central nervous system (CNS), which includes the brain and the spinal cord. Moderate doses of chemotherapy administered intravenously are ineffective in reaching the CNS, which is shielded from toxins by the blood-brain barrier, so physicians may administer chemotherapy directly to the spinal column (intrathecally), into the fluid that bathes the spinal cord and brain. Additionally, radiation is generally given to the brain and to any parts of the spinal cord affected by leukemia cells.
Bone Marrow Transplant
For some patients with AML a bone marrow or stem cell transplant may be part of the treatment plan. For more information on transplantation, visit our transplant section on the Web site.
Researchers at Memorial Sloan Kettering continue to develop new agents for cancer treatment, and to test new treatment approaches in our clinical trials. Relying in part on the information that is emerging about the genetic basis of leukemia, investigators are pursuing a variety of strategies to control the disease — approaches that can kill tumor cells directly, inhibit the body’s production of substances that promote their growth, or enhance the immune response against leukemic cells.
Chemotherapy drugs work in different ways to stop tumor cells from dividing and to prompt them to undergo programmed cell death, or apoptosis. Physicians are studying new drugs to see how effective they are in killing leukemia cells. If a new drug appears promising, often then it is combined with other agents in an effort to kill as many tumor cells as possible. Through studies such as these, physicians hope to find new, more-effective treatments for AML.
Monoclonal antibodies are genetically engineered proteins designed to target specific sites called antigens located on the surface of tumor cells. They can kill a targeted tumor cell by stimulating the normal immune system to destroy it or by blocking key mechanisms needed for the survival of cancer cells. Researchers at Memorial Sloan Kettering have pioneered this approach for the treatment of AML. A monoclonal antibody that binds to a protein called CD33, which is found on the surface of myeloid leukemia cells, has produced remissions in patients with AML. CD33 is currently being studied alone and in combination with low-dose chemotherapy. This treatment strategy may be particularly useful for patients who are unable to undergo intensive high-dose chemotherapy regimens. Additionally, monoclonal antibodies may serve as vehicles to deliver a radiative substance, chemotherapy, or toxin to a cancer cell. Investigators at Memorial Sloan Kettering have used antibodies to deliver radioactive metals that emit short-range high-energy alpha particles to tumor cells and are currently studying this approach in patients with AML.
Another promising area of research is the development of drugs that target mutated genes in leukemia cells, which are responsible for continued growth of the cancer. One promising target is a specific mutation in a gene known as FLT3, found on the leukemic cells of one-third of all AML patients. This mutation causes a particular enzyme involved in cell growth to be produced continuously, and this enzyme is responsible for the unchecked growth of blasts (immature cells) in AML. Investigators at Memorial Sloan Kettering have conducted clinical trials of experimental agents that block the action of this gene and will soon be examining these drugs in combination with standard chemotherapy drugs.
Acute leukemic cells have lost the ability to undergo programmed cell death, or apoptosis. Researchers know that agents such as retinoic acid work by forcing the malignant immature cells to differentiate, meaning that they proceed through their life cycle, mature, and then die. At Memorial Sloan Kettering, scientists and clinicians are collaborating in the search for new differentiation agents that will force leukemic cells to mature and die.
Researchers at Memorial Sloan Kettering are evaluating the effectiveness of vaccines made from protein pieces (peptides) found on AML cells that the immune system recognizes as abnormal. The studies are designed to see if these vaccines can trigger an immune response in patients with AML and other types of cancer that contain the abnormal protein.