Leukemia

Leukemia is a cancer of the bone marrow, the spongy center of the bones that makes blood cells. In leukemia, abnormal white blood cells divide out of control and crowd out the normal cells in the bloodstream. The abnormal white blood cells are not mature, and therefore cannot carry out their infection-fighting function in the blood. These cells crowd out healthy white blood cells, as well as the red blood cells which carry oxygen to the body and the platelets which cause the blood to clot.
What are the different types of childhood leukemia?
The most common type of leukemia in children is acute lymphocytic (or lymphoblastic) leukemia or ALL, which is further characterized as pre-B, B, or T-cell ALL. Childhood acute myeloid leukemia or AML is less common. "Acute" means that the diseases progress rapidly. The chronic forms of these leukemias, CLL and CML respectively, are seen almost solely in adults. In general, acute leukemias are most prevalent in children and are therefore often referred to as "childhood leukemias".
ALL: acute lymphocytic leukemia (pre-B, B, or T-cell). ALL NCI PDQ
AML: acute myeloid leukemia AML NCI PDQ
About 5% of childhood leukemias are distinct types of chronic myeloid leukemias. Juvenile myelomonocytic leukemia (JMML, NCI PDQ) occurs primarily in children aged 2 or under. Acute promyelocytic leukemia (APL, NCI PDQ) is a distinct subtype of AML. A good starting point for research into these and other less common childhood leukemias is on the cancer.gov myeloid leukemias page.
Types of white blood cells
White blood cells - the blood cells that grow out of control in leukemia - are the cells that fight infection. Blood contains three types of cells:
red blood cells (RBCs, or erythrocytes): these cells carry oxygen to all parts of your body and give the blood its red color
platelets (thrombocytes): these cells cause your blood to clot when you bleed
white blood cells (WBCs, or leukocytes): these cells defend your body from infections
All blood cells originate in the bone marrow. In fact, they all develop from one special type of cell, called a stem cell.
White blood cells come in several types, including:
granulocytes: fight bacteria by surrounding them and "eating" them.
monocytes: fight germs, but aren't as specific as granulocytes.
B-lymphocytes: these cells attach antibodies on germs (or anything they don't think belongs) with antibodies, which in turn signal other WBCs to get the tagged germ.
T-lymphocytes: these cells signal orders to other WBCs to come to a germ, and they make those other WBCs stay at the battle sight.
In acute lymphocytic leukemias, the B- or T-lymphocytes are growing out of control. In acute myelogenous leukemias, the granulocytes are growing out of control.
lymphocytic (ALL): uncontrolled growth of B- or T-lymphocytes
myelogenous (AML) (granulocytic): uncontrolled growth of granulocytes
In all of the leukemias, immature white cells crowd out the good cells. Since they crowd out the red blood cells, a person with leukemia is anemic, without enough red blood cells to carry the necessary oxygen or energy to the body. That's why fatigue is a sign of leukemia. The leukemia cells also crowd out the platelets, so if a person with leukemia is cut, the bleeding does not stop as readily. They also bruise easier. Since the blasts are immature, non-functioning infection fighting cells, a person with leukemia is easily susceptible to infection.
If you are interested in more information on blood cells, follow the links below for in-depth, technical information.
University of Virginia's site on blood cells - a good tutorial from the University of Virginia.
University of Washington REAL classification of leukemia cells, flow cytometry panels, diagnosis of acute leukemia, tdt, descriptions of many diagnostic tests used in leukemia treatment. From the University of Washington, Department of Laboratory Medicine, Hematopathology Laboratory.
Leukemia at Tulane University Medical Center. Photos of blood slides. Good information on the different types of blood cells on the hematopathology main page.
Treatment for childhood leukemias
ALL. The primary treatment for newly diagnosed ALL is combination chemotherapy. Radiation and bone marrow transplantation may be used in some cases. Treatment begins with an intense treatment called "induction" with a combination of several chemotherapy drugs, usually cytosine arabinoside, vincristine, prednisone, L-asparaginase, and daunorubicin. The goal of induction is to kill most of the leukemia cells; most patients do not have any leukemic cells in the bone marrow at the end of induction. (At least, not detectable in a light-microscopical examination of stained bone marrow smear.) The next phase is called "consolidation" in which a different combination of drugs is administered, usually methotrexate, cyclophosphamide, cytosine arabinoside, mercaptopurine, and prednisone. "Maintenance" follows, in which the chemotherapy is lessened to a few of the drugs administered less frequently. Maintenance is generally well tolerated by the patient. Often a period of maintenance is followed by another cycle of induction-consolidation, called "re-intensification". Total therapy lasts from two to three years. Detailed information on this web site:
ALL clinical trials page and ALL main page on this ped-onc site
AML. In general, newly diagnosed AML is initially treated more aggressively than is ALL. Intensive chemotherapy followed by bone marrow transplantation is becoming the first treatment chosen, especially when a suitable donor is available. After the intensive chemotherapy and/or bone marrow transplant, children with AML do not go on maintenance; studies have shown that AML children in remission have had as much chemotherapy as their bodies can tolerate, and additional maintenance chemotherapy does not benefit them.
Chronic myeloid leukemias. As in AML, intensive chemotherapy and/or BMT are generally employed. Currently (2005), imatinib mesylate (Gleevec) is being studied in clinical trials. Chronic leukemias have three clinical phases: chronic, accelerated, and blast crisis. Prognosis depends on the clinical phase of the disease.
Relapsed leukemia. Relapse, or recurrence of leukemia, can occur anytime during therapy or after completion of treatment. Generally, it is more difficult to cure a child after relapse of the leukemia; relapse during or soon after the completion of treatment is considered less favorable than relapse a year or several years after treatment. Treatment depends on the site of relapse, whether it is in the bone marrow, central nervous system, testes, or other locations. Aggressive chemotherapy and radiation treatment, often followed bone marrow transplantation, are used to treat relapse of childhood leukemia.
New Treatments
What's on the horizon for leukemia treatment? The following organization talks about new treatments:
Research updates from the Leukemia and Lymphoma Society
The big news (early 2000s) for the treatment of CML (and maybe Ph+ ALL) is STI-571. Brian Druker (Oregon Health Sciences University in Portland) is the Leukemia and Lymphoma Society doctor prominent in this research.
STI-571, now called Gleevec or imatinib mesylate
Gleevec web site
In 2004, ara G entered the treatment plans for T-cell ALL. Clofarabine (2005) shows promise for refractory (relapsed) ALL. More information in an essay on your author's private web site:
from sea to ara c
Statistics
Leukemia accounts for approximately 35% of all childhood cancers
Approximately 1 in 1000 children will be diagnosed with leukemia by the age of 19
It is more common in children under the age of 10
The five year survival rate for children diagnosed with leukemia and subsequently treated is approximately 70%
2500 cases of leukemia are diagnosed per year in the US

Article from :
http://www.acor.org/ped-onc/diseases/leuk.html