AML | ALL | CML

ACUTE MYELOGENOUS LEUKEMIAS

Induction

Initially the purpose of therapy is to reduce the circulating numbers of leukemia cells and induce a remission. This first line of therapy is known as Induction therapy. Induction therapy for the acute myelogenous leukemia varies depending upon the specific subtype of leukemia, however a typical course runs about a month.

For induction therapy to be given, patients often have a central venous catheter also known as a vascular access device placed. The catheter allows for the infusion of chemotherapy, intravenous fluids, antibiotics and blood products, and the withdrawal of blood for testing.

Therapy usually consists of two drugs – the first is cytosine arabinoside ( ARA-C) the second is usually either daunorubicin or idarubicin. These drugs are administered intravenously. Treatment approaches for leukemia are continuously being evaluated therefore drug combinations, and sequences may be different if patients are participating on a clinical trial.

Vulnerability to infections

After the completion of the induction chemotherapy patients may have very low blood cell counts for up to 2-4 weeks.  This is caused by the chemotherapy destroying healthy cells as well as leukemia cells. During this time, patients are at an increased risk of developing infections or bleeding. Patients often require support with antibiotics, antivirals, antifungals, and blood and platelet transfusions, to support them during this time.

Generally, patients’ blood counts return to normal levels during this 2-4 week time period. The period of time from administration of the chemotherapy to the recovery of the blood counts is all part of  “the induction.”

Remission

When patients’ blood counts return to their normal levels, a bone marrow aspirate and biopsy is repeated looking for leftover or residual leukemic cells. If none are detected,  patients are considered in remission. Remission is defined as no detectable leukemic cells in the bone marrow, and peripheral blood counts have returned to normal. In the event a remission is not achieved after induction, re-induction therapy is given.

Consolidation

Even if the marrow and blood appear free of leukemic cells, it’s generally assumed an undetectable but substantial burden of leukemia cells remains. To prevent a relapse or recurrence within a few weeks of first remission, “consolidation therapy” is undertaken.  Post-remission, or consolidation therapy is indicated with the goal of eradicating other undetectable leukemia cells. 

Consolidation therapy differs depending on a patient’s age, overall health including other medical conditions such as heart disease, diabetes, or lung disease, and the cytogenetics of their leukemia.  During consolidation therapy patients receive dose intensive therapy, often with cytosine aribonoside(ARA-C). Other options at this time are autologous or allogeneic blood or marrow transplantation.

The exception to this course of therapy is Acute Promyelocytic Leukemia.

APL represents about 8-15% of all newly diagnosed cases of leukemia, and has favorable prognostic indicators. APL usually presents with a structural rearrangement involving chromosomes 15 and 17, and may present with a coagulation disorder at diagnosis (DIC). Characteristically,  APL cells stop short during their differentiation process, and do not fully mature. Trans-retinoic acid (a derivative of vitamin A) brings on maturation in these APL cells, therefore reducing the leukemia burden in the blood and bone marrow. Often patients achieve remissions with trans-retinoic acids alone, however to insure long-term remission, chemotherapy with trans-retinoic acid or other chemotherapy agent may be administered

ACUTE LYMPHOBLASTIC LEUKEMIA

Induction

Induction therapy for ALL is similar to that for AML but it usually consists of many drugs. Patients require the placement of a central venous catheter even though some chemotherapy agents may be given orally.

Because ALL often involves the central nervous system, many patients require intrathecal chemotherapy as well, and or radiation to the cranium(head) and spine. 

After the induction therapy is complete, patients are vulnerable to infection and bleeding because the chemotherapy destroyed healthy cells as well as leukemia cells.  Patients often require support with antibiotics, antivirals, antifungals, and blood and platelet transfusions, to support them during this time.

When patients’ counts recover, a bone marrow aspirate and biopsy is performed to look for any residual disease.  If no leukemia cells are detected, patients are considered in remission.

Consolidation can last three years.

In order to maintain this remission, patients with ALL require numerous consolidation courses, including intrathecal maintenance, which may last for up to three years.  During this post-remission therapy, patients’ overall health, remission status including cytogenetics, and the feasibility of a blood or marrow transplant are evaluated.

CHRONIC MYELOGENOUS LEUKEMIA

Treatment for CML is dictated by the symptoms a patient is experiencing, and the results of the blood and bone marrow tests.

The only known “cure” for CML is an allogeneic blood or marrow transplant, from a related donor or unrelated donor.  (see Transplant Center)

Treatment for CML is usually initiated once the diagnosis, and the cytogenetics of the patient have been established. Patients who are under 60 years old should have a bone marrow or stem cell transplant consultation.

Chemotherapy and immunotherapy are used to treat CML when no available transplant donor is found, or a transplant is not suggested for other health reasons.

Drugs used to control elevated white blood cell counts, and platelet counts are interferon, hydroxyurea (hydrea), anagralide, and  busulfan.

Other therapies such as leukapheresis  and platelet pheresis can be done to lower these counts, but are not the recommended therapy of choice. 

Leukapheresis is a procedure in which white blood cells are removed from a person.  Blood is withdrawn from a patient and run through a machine which separates out the white blood cells. The patient’s blood, minus the white blood cells, is returned to the patient. Platelet pheresis is similar to leukaphereis except platelets are removed instead of white blood cells.

A new form of therapy for CML is designed to block certain proteins that are likely responsible for transforming a chronic phase blast cell into a blastic phase cell, it is known as STI-571. This drug and others are currently under investigation.  Should a patient with CML continue to have elevating blood cell counts and experience more symptoms, systemic chemotherapy may be recommended.

Written by Jane Quigley, RN, BSN, cancerpage.com
Edited by Mitchell S. Cairo, MD, Director of the Pediatric Blood and Marrow Transplant Program, Experimental Therapeutics and Hematopoiesis, and Pediatric Cancer Research Program at the Columbia University Medical Center, Babies and Children Hospital.