Targeted therapy for childhood leukemia
In recent years, new drugs that target specific parts of cancer cells have been developed.
These targeted drugs work differently from standard chemotherapy drugs. They
sometimes work when chemo drugs don’t, and they often have different (and less severe)
side effects. Some of these drugs can be useful in certain childhood leukemias.
For instance, nearly all children with chronic myeloid leukemia (CML) have an abnormal
chromosome in their leukemia cells known as the Philadelphia chromosome. Targeted
drugs such as imatinib (Gleevec) and dasatinib (Sprycel) specifically attack cells that
have this chromosome. These drugs are very effective at controlling the leukemia for
long periods of time in most of these children, although it’s not yet clear if the drugs can
help cure CML.
A small number of children with acute lymphocytic leukemia (ALL) also have the
Philadelphia chromosome in their leukemia cells. Studies have shown that their outcome
is improved when these drugs are given along with chemotherapy drugs.
These drugs are taken daily as pills. Possible side effects include diarrhea, nausea, muscle
pain, fatigue, and skin rashes. These are generally mild. A common side effect is swelling
around the eyes or in the hands or feet. Some studies suggest this fluid buildup may be
caused by the drugs’ effects on the heart. Other possible side effects include lower red
blood cell and platelet counts at the start of treatment. These drugs might also slow a
child’s growth, especially if used before puberty.
Other targeted drugs are now being tested in clinical trials as well.
For more general information on targeted drugs, see Targeted Therapy.
High-dose chemotherapy and stem cell transplant for
childhood leukemia
A stem cell transplant (SCT) can sometimes be used for children whose chances of being
cured are poor with standard or even intense chemotherapy. SCT lets doctors use even
higher doses of chemotherapy than a child could normally tolerate.
High-dose chemotherapy destroys the bone marrow, which is where new blood cells are
formed. This could lead to life-threatening infections, bleeding, and other problems
caused by low blood cell counts. A stem cell transplant is given after the chemo to restore
the blood-forming stem cells in the bone marrow.
The blood-forming stem cells used for a transplant can come either from the blood or
from the bone marrow. Sometimes stem cells from a baby’s umbilical cord blood are
used.
Allogeneic stem cell transplant
For childhood leukemias, the type of transplant used is known as an allogeneic stem cell
transplant. In this type of transplant, the blood-forming stem cells are donated from
another person.
The donor’s tissue type (also known as the HLA type) should match the patient’s tissue
type as closely as possible to help prevent the risk of major problems with the transplant.
Tissue type is based on certain substances on the surface of cells in the body. The closer
the tissue match between the donor and the recipient, the better the chance the
transplanted cells will “take” and begin making new blood cells.
The donor is usually a brother or sister with the same tissue type as the patient. Rarely, it
can be an HLA-matched, unrelated donor – a stranger who has volunteered to donate
blood-forming stem cells. Sometimes umbilical cord stem cells are used. These stem cells
come from blood drained from the umbilical cord and placenta after a baby is born and
the umbilical cord is cut. (This blood is rich in stem cells.) Whatever their source, the
stem cells are then frozen and stored until they are needed for the transplant.
To learn about how a stem cell transplant is done, see Stem Cell Transplant (Peripheral
Blood, Bone Marrow, and Cord Blood Transplants).