Wilms Tumor
The information in
this
article is meant to educate and should not be used as an alternative
for
professional medical care.
According to A
Parent's
Guide to Solid Tumor Cancers by Honna Janes-Hodder & Nancy
Wilms tumor is the second
most common type of all childhood solid tumors, not including brain
tumors. It
accounts for approximately 6 percent of all childhood cancers. The
average age
at diagnosis is between two and three years when the disease is
unilateral
(affecting only one kidney), but it is generally diagnosed at a younger
age in
children when the disease is bilateral (affecting both kidneys).
Seventy-five
to eighty percent are diagnosed before the age of five. Approximately
450 new
cases are seen annually in
Signs and symptoms
Wilms tumor is
often a
difficult disease to diagnose. Usually, a parent notices a lump or mass
in the
abdominal area while dressing or bathing her child who has no other
symptoms.
By this time, the tumor is generally very large. Sometimes the tumor is
found
during routine visits when the pediatrician palpates the toddler's
abdomen.
Wilms tumor is occasionally diagnosed when the child is evaluated for
other
unrelated reasons, such as accidental trauma to the abdominal area.
Some children with
Wilms
tumor have abdominal pain and up to 25 percent will have hematuria
(blood in
the urine). Blood may be visible to the naked eye or it may only be
seen with
microscopic evaluations. In addition, up to 25 percent of children have
high
blood pressure at diagnosis.
Other symptoms that may be present include fever,
diarrhea, weight loss,
shortness of breath, urogenital infections, and anemia (low number of
red
cells). The child may feel generally tired and unwell. Nausea and
vomiting are
infrequent symptoms of a Wilms tumor.
Several tests and
procedures
are necessary to diagnose Wilms tumor. The doctor will first perform a
physical
examination and obtain the child's medical history. This is usually
followed by
an abdominal ultrasound and/or a CT scan. Occasionally, a scan called
magnetic
resonance imaging (MRI) is done. Because some children with Wilms tumor
have
bilateral involvement, both kidneys need to be examined. A complete
blood count
(CBC) is ordered, as well as urinalysis to check for signs of hematuria
(blood
in the urine). Kidney function tests are also taken.
X-rays and CT scans
of the
chest should be ordered to determine if the disease has spread to the
lungs.
Approximately 10 percent of children with Wilms tumor have lung
metastases at
diagnosis.
A chemical survey of the blood
(called blood
chemistries) is done to establish baseline kidney function, since one
kidney is
usually removed as part of the treatment protocol. Chemical surveys
also check
for liver disease and elevated levels of urates and phosphate.
Staging
Once Wilms tumor
has been
diagnosed, surgery and/or more tests are done to determine if the
cancer has
spread to other parts of the body. This process is called staging and
it helps
the doctor choose the most appropriate treatment for the child.
Wilms tumor is
staged by the
following system, devised by the National Wilms Tumor Study Group
(NWTSG):
- Stage
I. The tumor is limited to
the kidney and is able to be completely removed surgically.
- Stage
II. The tumor extends beyond
the kidney, but it is able to be completely removed surgically.
- Stage
III. The tumor is not able to
be completely removed surgically or is spilled at surgery, but disease
is still limited to the abdomen.
- Stage
IV. The disease has spread
from the abdomen through the bloodstream and may be found in the lung,
liver, bone, or brain, as well as distant lymph nodes.
- Stage
V. The tumor is found on both
kidneys at the time of diagnosis.
Prognosis
Treatment of Wilms
tumor in
children is one of medicine's success stories. Due to improvements in
surgical
techniques, drug therapies, and radiation, 85 to 90 percent of children
with
Wilms tumor who receive state-of-the-art treatment are cured. The best
treatment for each child with Wilms is determined by analysis of
several
clinical and biologic features.
After a biopsy or surgery, the
pathologist
examines the nucleus of the cancerous cells under a microscope. If the
nuclei
of some of the cells appear larger than normal or irregular in shape,
it is
called anaplasia. Local anaplasia does not appear to affect prognosis.
If there
is a large proportion of anasplasia scattered throughout the tumor, it
is
called diffuse anasplasia and has a poorer prognosis.
Tumor cells that
are not
anaplastic are said to be Wilms tumor of favorable histology. The vast
majority, approximately 95 percent, of children diagnosed with Wilms
have cells
with a favorable histology
The oncologist will determine the prognosis using
many criteria, including
stage of disease, histology of the tumor cells, age of the child, and
size of
the tumor. These factors affect the aggressiveness of treatment needed.
For
example, a child diagnosed with stage II, favorable histology receives
less
intensive therapy than does a child with stage IV, unfavorable
histology.
The vast majority
of children
with Wilms who receive optimal treatment are cured of the disease. At
diagnosis, many parents are confused about how to find the best doctors
and
treatments for their child. State-of-the-art care is available from
physicians
who participate in the National Wilms Tumor Study Group, the Children's
Cancer
Group (CCG), and the Pediatric Oncology Group (POG). These study
groups,
composed of pediatric surgeons and oncologists, urologists, radiation
oncologists, researchers and nurses, establish the standard of care for
patients worldwide, conduct new studies to discover better therapies or
fine
tune old ones, and establish follow-up for survivors. They are in the
process
of merging into one entity called the Children's Oncology Group (COG).
If the
treatment center you are referred to is a member of one of these
groups, you
can rest assured that your child will have access to the best thinking
on the
treatment of pediatric cancers.
The doctor will choose the best
treatment or
clinical trial based on many factors, including your child's age, stage
of
disease, and size and histology of the tumor. For most patients,
treatment is
surgery followed by chemotherapy. Some children also require radiation.
Surgery
Children diagnosed
with Wilms
tumor usually have a surgical procedure, called a nephrectomy,
performed before
any other therapy is initiated. Occasionally, if the diagnosis is
questionable,
a biopsy will be performed prior to nephrectomy. In
There are three different types of
nephrectomies:
- Simple
nephrectomy. Removal of the
tumor as well as the entire kidney and ureter. The remaining kidney is
able to compensate for the loss.
- Partial
nephrectomy. Removal of the
tumor and a portion of the affected kidney. It is done usually if the
other kidney has already been removed or is damaged.
- Radical
nephrectomy. Removal of the
tumor, kidney, and some surrounding tissue.
During surgery, the
surgeon
evaluates the remaining kidney for disease and takes samples from lymph
nodes
in the area. The surgeon may also biopsy areas of the liver if she
suspects
that disease may be present.
Chemotherapy
All children
diagnosed with
Wilms tumor receive chemotherapy (drugs that kill cancer cells) as part
of
their treatment protocol.
There are several chemotherapy drugs
that are
effective against this type of cancer. The use of dactinomycin and
vincristine
has dramatically increased survival rates. Children with early stage
disease
often are treated with just these two drugs. For those who are
diagnosed at
more advanced stages, doxorubicin, cyclophosphamide, etoposide,
ifosfamide, and
carboplatin may be added.
Radiation
The decision to use
radiation
therapy to treat a child with Wilms is based largely on the stage and
histology
of the tumor. Children with stage I and stage II favorable histology
disease do
not require radiation. For children with more advanced stages of
disease,
external beam radiation therapy is given. This type of treatment uses
high
energy rays, delivered from outside the body, to kill cancer cells. The
amount
of disease present will determine the size of the area to be radiated.
Usually,
1000 cGy, with an optional 1000 cGy boost to the tumor, is the
recommended dose
of radiation given to children with advanced stage diseases or tumors
with
unfavorable histology.