- What is acute lymphoblastic leukemia (ALL)?
Acute lymphoblastic leukemia (ALL) is a cancer of the white blood cells,
the cells in the body that normally fight infections. There are two main
types of white blood cells—lymphoid cells and myeloid cells. ALL affects
lymphoid cells.
Leukemia cells are abnormal cells that cannot do what normal blood cells
do. The abnormal cells are immature white blood cells that cannot help the
body fight infections. For this reason, children with ALL often get infections
and have fevers.
ALL is also called acute lymphocytic leukemia. It is the most common leukemia
in children.
- What are the symptoms of ALL?
Like all blood cells, leukemia cells travel through the body. Depending
on the number of abnormal cells and where these cells collect, patients
with leukemia may have a number of symptoms. Children with ALL frequently
have low amounts of healthy red blood cells and platelets. As a result,
there are not enough red blood cells to carry oxygen through the body. With
this condition, called anemia, patients may look pale and feel weak and
tired. When there are not enough platelets, patients bleed and bruise easily.
Some of the common symptoms of ALL include:
In ALL, the abnormal cells may collect in the brain or spinal cord, also
called the central nervous system (CNS). The result may be headaches
with or without vomiting, although most children with the disease do not
have these symptoms. Leukemia cells also can collect in the testicles and
cause swelling.
- Is there a screening test for ALL?
No. Screening is a means of detecting disease in people who have no symptoms.
As described in the National Cancer Institute's Cancer
Screening Overview (PDQ®) (http://www.cancer.gov/cancertopics/pdq/screening/overview/healthprofessional), two requirements must be met for screening to be useful:
(1) There must be a test or procedure that will detect cancers earlier
than if the cancer were detected as a result of the development of symptoms,
and
(2) There must be evidence that treatment initiated earlier as a consequence
of screening results in an improved outcome.
These two requirements have not been met for childhood ALL.
In cancers such as leukemia that appear throughout the body during their
earliest stages, screening does not appear to be useful. Rather, children
with any symptoms that suggest the possibility of ALL should be seen by
their physician. The physician can then examine the child and determine
if further testing is needed.
- How is ALL diagnosed?
If a child has symptoms that suggest leukemia, the physician may first
order blood tests. A sample of blood is examined to determine the number
of normal blood cells, to see what the cells look like, and to find out
if any leukemia cells are present in the blood. For a definitive diagnosis
of ALL, a doctor who specializes in leukemia examines a sample of bone marrow
under a microscope. The sample is obtained by a procedure called bone marrow
aspiration. In this procedure, the doctor inserts a needle into a large
bone, usually the hip, and removes a small amount of liquid bone marrow
for examination.
If leukemia cells are found in the bone marrow sample, the patient's doctor
orders other tests to find out the extent of the disease. For example, a
spinal tap, which is also called a lumbar puncture, checks for leukemia
cells in the cerebrospinal fluid—the fluid that fills the spaces in
and around the brain and spinal cord.
- Are there different types of ALL?
Although leukemia cells from different children with ALL often look very
similar under the microscope, there are actually many distinctive subtypes
of ALL. Most cases of leukemia are associated with changes in genes and
chromosomes in the cancerous white blood cells. The various subtypes of
ALL can be identified using special laboratory tests that look for specific
changes in genes and chromosomes. It is increasingly important for doctors
treating children with ALL to determine their patients' subtype of ALL,
as some treatments work better for some subtypes than for others.
- How common is ALL?
Cancer in children and adolescents is rare. But, ALL is the most common
cancer in children, representing 23 percent of cancer diagnoses among children
younger than 15 years of age. It occurs in about one of every 29,000 children
in the United States each year.
- What causes ALL?
With the exception of prenatal exposure to X-rays and specific genetic
syndromes, such as Down syndrome, little is known about the causes of and
risk factors for childhood ALL.
Scientists know that ALL in children occurs slightly more often in boys
than in girls and in white children more often than in black children. However,
they cannot explain why one person gets leukemia and another does not.
- What treatments are available for the disease?
There are treatments
for all children with ALL (see http://www.cancer.gov/cancertopics/pdq/treatment/childALL/healthprofessional).
The primary treatment for ALL is chemotherapy. The specific drugs used for
chemotherapy are different for the various subtypes of ALL and are not the
same for all patients.
Treatment for children with ALL is complex and involves multiple drugs
given in precise schedules over a period of two to three years. Because
of this, children with the disease should be treated by doctors with experience
and expertise in the treatment of childhood leukemias.
Many children with ALL participate in clinical
trials. These studies test a new drug or a new combination of drugs,
often comparing them to the current standard treatment. A participant will
usually be assigned to the standard group or the new group by chance, a
process called randomization. It is not known at the start of the trial
whether the new treatment is better than, the same as, or worse than the
standard treatment. Clinical trials for children with ALL often enroll large
numbers of children and are conducted at children's cancer centers nationwide.
Much of the success in curing children with ALL is the result of better
treatments that were identified in such clinical trials. Still, doctors
are doing clinical trials to try to improve ALL treatments and reduce side
effects.
- What is the survival rate for children with ALL?
The improvement in survival for children with ALL over the past 35 years
is one of the great success stories of cancer treatment. In the 1960s, less
than 5 percent of children with ALL survived for more than five years. Today,
about 85 percent of children with ALL live five years or more.
- What factors determine successful treatment for children with ALL?
The chance of survival for children with ALL is dependent upon a number
of factors. The most important factor is receiving optimal care at a center
experienced in the treatment of children with ALL. Even with optimal care,
some children with ALL are much more difficult to treat successfully than
others.
In the past, factors such as age and white blood cell count at diagnosis
were commonly used to predict outcome. For example, children 1 to 9 years
old have higher survival rates than do infants or older children. However,
factors such as age and white blood cell count at diagnosis are, at best,
crude predictors of outcome.
It is now clear that the patient's subtype of ALL has a powerful impact
on survival. For example, infants commonly have a subtype of ALL in which
a specific gene is modified. This subtype of ALL is very hard to treat successfully
and only a minority of infants with this subtype of ALL survive with current
therapy. Other subtypes of ALL in which different genes are modified occur
more commonly in older children and have a much more favorable outcome.
It is now common practice for the leukemia cells of children with ALL to
be tested for the gene modifications. The type of treatment is then based
on the particular change seen in the leukemia cells.
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