Wilms Tumor

What Is Wilms Tumor?

Wilms tumor (also called Wilms' tumor or nephroblastoma) is the most common type of kidney cancer in children. Most kinds of cancer are named for the place where the cancer starts. Although Wilms tumor starts in the kidney, it is named for the German doctor (Max Wilms) who first wrote about it in 1899. About 90% of kidney cancers in children are Wilms tumors.

About the Kidneys

The kidneys are 2 curved organs in the abdomen. Each kidney is about the size of a fist. One kidney is just to the left and the other just to the right of the backbone. The lower rib cage protects the kidneys.

The kidney's main job is to filter the blood and get rid of extra water, salt, and waste products in the form of urine. Urine leaves the kidneys through long slender tubes called ureters. Each kidney has a single ureter. The ureters empty into the bladder where urine is stored until you urinate. Although the kidneys are important, people can get by with just a single kidney. Many people are living normal, healthy lives with just one kidney.

Wilms tumors usually form only in 1 kidney, but in a small number of cases they can form in both. Wilms tumors are often found only after they have grown quite large. But most are found before they have spread to other organs. The average weight of a newly-found Wilms tumor is about a pound. That's larger than the kidney it started in.

Types of Wilms Tumors

There are 2 main types of Wilms tumors. Doctors look at cells from the tumor through a microscope to decide which type it is.

• Wilms tumor of favorable appearance under the microscope
• Wilms tumor of unfavorable appearance under the microscope

If a tumor has an unfavorable appearance (histology), it means that the center of the cells (the nucleus) is very large and not the right shape. This is called anaplasia. The more anaplasia is found, the worse the chance for a cure. A favorable appearance means there is no anaplasia and the chance of cure is good. About 95% of Wilms tumors have a favorable appearance.

Rarely, children can have other kinds of kidney cancer. The information here applies only to Wilms tumor and not to other kinds of kidney cancer.

What Causes Wilms Tumor? Can It Be Prevented?

Researchers are learning more about how changes in the genes and other factors work together to cause Wilms tumors and other cancers. Although they don't know exactly why some children get Wilms tumors, they have made great progress in understanding what happens as the kidneys form in a fetus. When this process goes wrong, Wilms tumor can be the result.

The kidneys develop very early as babies grow in the womb. Sometimes a mistake happens as the kidney grows. Some of the cells don't mature. Instead, they remain as early (fetal) cells. Small or large clusters of these early kidney cells can still be there after the baby is born. Most often, these cells will mature by the time the child is 3 or 4 years old. But if this doesn't happen, the cells may begin to grow out of control. The result could be a Wilms tumor.

A risk factor is something that is linked to a greater chance of getting a disease. Some risk factors, such as smoking, can be controlled. Others, like a person's age or race, can't be changed. Different cancers have different risk factors. Most of the risk factors for Wilms tumor cannot be controlled. They are genetic or hereditary (inherited).

A small number of children with Wilms tumor have a relative with the same cancer. These children may have inherited an abnormal gene from one parent. This gene increases the risk of Wilms tumor, but it does not mean the child will have Wilms tumor.

There is a strong link between Wilms tumors and certain kinds of birth defects. Most birth defects linked to Wilms tumors occur in syndromes. Syndromes are groups of symptoms or conditions that often occur together in the same person. Several different syndromes are linked to Wilms tumors. These syndromes are associated with certain changes in genes. A part of a gene or even a whole gene may be missing. These missing or changed genes can cause Wilms tumors and other birth defects.

But most children with Wilms tumors do not have any known gene changes or birth defects. We cannot explain why they develop these tumors. There is nothing their parents could have done to prevent the cancer.

Can Wilms Tumor Be Prevented?

Right now there is no known way to prevent Wilms tumors. Experts think the cancer comes from cells that were in the fetus, but failed to develop into mature kidney cells. This doesn't seem to be caused by anything that a mother could avoid.

How Is Wilms Tumor Found?

Children who have birth defects known to be linked to Wilms tumor should be checked regularly. The doctor will schedule physical exams and other tests to watch for signs of a tumor. Ultrasound exams are usually done every 3 months until the child is 6 or 7 years old. You should tell your doctor if you have family members who have had Wilms tumor. If so, the other children in the family may need to have regular tests.

There are no blood tests or other tests to look for Wilms tumors in otherwise healthy children.

Symptoms of Wilms Tumor

Wilms tumors can be hard to find early. They sometimes grow quite large without causing any pain. Children may look healthy and seem normal. The first sign is usually a large lump in the belly. Chances are parents will notice the swelling. Some children may also have other symptoms such as:

• stomach pain
• fever
• blood in the urine
• high blood pressure

If your child has these symptoms, see a doctor right away.

If there is any reason to suspect Wilms tumor, the doctor will ask questions to check for risk factors and symptoms. A physical exam can provide information about possible signs of Wilms tumor and other health problems. After that, the doctor may want to conduct certain tests to find out if the disease is present.

Imaging Tests

Ultrasound: This test uses sound waves to create a picture of the inside of the body. The echoes made by most kidney tumors differ from those of normal kidney tissue. This is often the first test done they suspect your child has Wilms tumor. An ultrasound is painless and allows the doctor to see the entire abdomen.

CT (computed tomography) scan: This scan uses x-rays to take many pictures of the body that are then combined by a computer to give a detailed cross-sectional image. A CT scan is one of the most useful methods of finding a mass inside the kidney. It is also useful to see whether the cancer has spread beyond the kidney.

MRI (magnetic resonance imaging): MRI uses radio waves and strong magnets instead of x-rays. Like CT scans, MRIs display a cross-section of the body but in greater detail, which can help doctors see if the cancer is in one of the major blood vessels near the kidney.

Angiography (an-jee-og-ruh-fee): In this test, a contrast dye is injected into the artery leading to the kidney. The dye outlines the blood vessels on x-ray pictures. This is useful in helping the surgeon plan an operation.

Chest x-rays: Chest x-rays are used to see whether the Wilms tumor has spread to the lungs.

Bone scan: For this test, a small amount of radioactive material is injected into a vein. The material collects in areas of diseased bone and can be seen with a special camera. This can help find cancer that has spread to the bones.

Other Lab Tests

Certain blood tests are done to count the number of white blood cells and red blood cells and to measure other substances in the blood. Urine may be tested as well. Although these tests are not used to find Wilms tumor, they do give clues about how well the liver and kidneys are working.

How Is Wilms Tumor Treated?

This information represents the views of the doctors and nurses serving on the American Cancer Society's Cancer Information Database Editorial Board. These views are based on their interpretation of studies published in medical journals, as well as their own professional experience.

The treatment information in this document is not official policy of the Society and is not intended as medical advice to replace the expertise and judgment of your cancer care team. It is intended to help you and your family make informed decisions, together with your doctor.

Your doctor may have reasons for suggesting a treatment plan different from these general treatment options. Don't hesitate to ask him or her questions about your treatment options.

More than 90% of children with Wilms tumor are cured. Much of the progress in treatment has happened because of the work of the National Wilms Tumor Study Group (now part of the Children's Oncology Group). This group organizes clinical trials of new treatments for most children with Wilms tumor in this country.

After your child's Wilms tumor is found and staged, the doctor will suggest a treatment plan. Today, most children with this cancer are treated as part of a clinical trial to try to further improve on what doctors believe is the best treatment.

Because Wilms tumor is rare, few doctors except those in children's cancer centers have much experience in treating these children. A team approach that includes the child's pediatrician as well as experts at the cancer center is recommended. If you decide to get a second opinion, it should be done quickly because Wilms tumor is usually very large and tends to grow fast.

Treatment for Wilms tumor usually involves surgery, chemotherapy, and sometimes radiation. The first goal of treatment is to remove the primary tumor even if there are distant areas of spread (metastases). If any cancer remains after the first operation, radiation therapy or more surgery might be needed.

Sometimes the tumor may be too large to remove. It may have spread into nearby blood vessels or other vital structures, or it may be in both kidneys. In these cases, doctors might use chemotherapy or radiation therapy (or both) to shrink the tumor before removing it.

Surgery

Surgery is the main treatment for Wilms tumor. It should be done by a doctor who specializes in operating on children. Also, it's better if the surgeon has experience in treating children with cancer.

The most common operation is a radical nephrectomy (nuh-frek-tuh-me). The cancer and the whole kidney are removed as well as the ureter, the adrenal gland, and some fatty tissue around the kidney. The surgeon may also remove lymph nodes (small, bean-sized collections of immune system cells that help the body fight infections) next to the kidney since cancer often spreads to these nodes.

During surgery the doctor will look at the liver and the other kidney and perhaps take samples of any suspicious areas. These will be looked at under a microscope to see if they contain cancer cells. If an x-ray or scan suggests that the cancer might have spread to the lungs, then the doctor may also take a sample of lung tissue. Knowing whether or not a Wilms tumor has spread is important in determining its stage and choosing a treatment.

Often, if chemotherapy is to be given, the surgeon will insert a small plastic tube (called a venous access device) into a large blood vessel. The end of the tube is under the skin of the chest area or upper arm. This cuts down on the number of needle sticks needed to take blood samples for tests and to give medicines and blood transfusions. Someone will teach you how to care for your child's device.

Chemotherapy

Chemotherapy refers to the use of drugs to kill cancer cells. Usually the drugs are given into a vein, by mouth, or through a venous access device. Once the drugs enter the bloodstream, they reach throughout the body. This makes chemotherapy especially useful for cancer that has spread beyond the kidney.

Chemotherapy drugs are given in different combinations and strengths and at different times, depending on the stage of the tumor. They are usually given by a nurse in the doctor's office or in the outpatient section of the hospital.

These drugs can have some side effects, depending on the type of drug, how much is given, and for how long. Temporary side effects could include the following:

• nausea and vomiting
• loss of appetite
• mouth sores and pain
• constipation
• pain in the arms, legs, and jaw
• weakness, tingling, numbness in the arms and legs
• diarrhea
• hair loss (the hair grows back after treatment ends)
• an increased chance of infection (from a shortage of white blood cells)
• bleeding or bruising after minor cuts or injuries (from a shortage of blood platelets)
• tiredness or shortness of breath (from low red blood cell counts)

These side effects go away when treatment is over, but be sure and talk to the doctor if your child has problems. Often there are ways to lessen these. For example, there are drugs that can be taken at the same time as the chemotherapy to lessen or prevent mouth pain, nausea, and vomiting.

There are other risks as well. One type of drug can sometimes damage the heart. Your child's doctor will check for this possibility with heart studies. Chemotherapy can also increase your child's risk of getting a second type of cancer in the future. But the importance of treating Wilms tumor far outweighs these risks.

Radiation Therapy

Radiation therapy is treatment with high energy rays (such as x-rays) to kill or shrink cancer cells. External beam radiation is given in a way similar to that used to find broken bones. This type of radiation is often used along with surgery for stages III, IV, or V Wilms tumor. It is generally not used for stages I or II unless it is stage II with an unfavorable appearance (histology).

Side effects from radiation can include nausea, diarrhea, tiredness, and sunburn-like skin changes. Often, these will go away after a short while. Radiation can also cause a second cancer to develop or can damage other organs or tissues that are in the radiation field. But this usually doesn't happen because the amount of radiation used is low.

Recurrent Wilms Tumor

The outlook for children whose tumor comes back depends on what treatment they first had and the cancer's histology. The outlook is better for children with a favorable histology who did not have abdominal radiation. The recurrent cancer is then treated with surgery, radiation, and more chemotherapy.

The outlook is often poor for children with recurrent Wilms tumor with any of the following features:

• unfavorable histology
• earlier treatment with radiation therapy
• chemotherapy with the drug doxorubicin
• recurrence within 6 months of the first surgery
• failure of the tumor to completely disappear with the first treatment

Treatment for these children usually involves strong chemotherapy, often with new drugs being studied in clinical trials. Very high-dose chemotherapy with a bone marrow transplant may also be an option.

Most parents find it stressful to watch their child go through cancer treatment. Sometimes this will lead to a minor form of what is called post traumatic stress disorder or PTSD. Parents might find they are irritabe and have outbursts of anger. It may also affect the child's treatment, because parents with this problem will try to avoid the thing that is causing the problem, namely their child's treatment. If you find that you are having trouble coping with your child's illness or treatment, talk to your child's doctor and ask for help in dealing with the problem.

Survival Rates for Wilms Tumor

The 5-year survival rate for children with Wilms tumor varies with the stage of the tumor. It also depends on the histology (appearance) of the tumor cells under a microscope. These rates refer to the percentage of patients who live at least 5 years after their cancer is found. Most of these patients are cured. Ask your doctor to explain the stage and the histology of your child's cancer.

These numbers provide an overall picture, but keep in mind that every child's situation is unique and the statistics can't predict exactly what will happen. Talk with your cancer care team if you have questions They know your child's situation best.

Stage	Favorable histology	Unfavorable histology
I	96%	93%
II	91%	70%
III	91%	56%
IV	81%	17%
V	82%	(unknown)