Wilms' Tumor: What you need to know

Wilms' tumor, also known as nephroblastoma, is a rare type of kidney cancer. It usually affects children before the age of 6 years. It is very rare in adults.

Named after Max Wilms, a German doctor who first described it in 1899, it is the most common kidney tumor in those aged under 15 years.

This article will cover basic information on Wilms' tumors, what they are, the signs and symptoms, diagnosis, and treatment.

What is a Wilms' tumor?

Wilms' tumors are rare, but they are the most common malignant tumors of the kidneys in children. If a tumor appears in a child, there is a 90-percent chance that it will be a Wilm's tumor.

They occur around the ages of 3 to 4 years and only very rarely after the age of 6 years. About 500 cases are reported in the United States each year.

Over three-quarters of cases occur in otherwise healthy children, while one quarter are linked to other developmental problems.

Treatment usually has a high success rate. Over 90 percent of those who undergo treatment will survive at least 5 years.

In 95 percent of cases, the tumor affects one kidney, although there may be more than one tumor. In 5 percent of cases, it affects both kidneys. It is thought to develop from immature kidney cells.

The tumors are believed to result from the loss or inactivation of a tumor suppressor gene called QT1 on chromosome 11. Tumor suppressor genes usually hold back tumor growth and control cell growth.

Symptoms

During the early stages, there may be no symptoms at all, and even a fairly large tumor may be painless. However, even large tumors are usually found before they start to metastasize, or spread to other parts of the body.

If symptoms occur, there may be:

• a swelling in the abdomen
• blood in the urine and abnormal urine color
• fever
• poor appetite
• high blood pressure
• abdominal or chest pain
• nausea
• constipation
• large and distended veins across the abdomen
• malaise, or feeling unwell
• vomiting
• unexplained weight loss

If the tumor has spread to the lungs, there may also be coughing, blood in the sputum, and difficulty breathing.

Treatment

Treatment for Wilms' tumor depends on several factors, including:

• age
• overall health
• medical history
• the extent of the condition
• tolerance to certain medications or procedures
• parental preferences

Standard treatment usually involves surgery, chemotherapy, and sometimes radiation therapy.

Wilms' tumor is rare, and the doctor may advise that treatment be done at a pediatric cancer center.

Surgery

Options include nephrectomy, which is the surgical removal of kidney tissue.

Simple nephrectomy: The whole kidney is surgically removed. The other kidney is enough to maintain the patient in good health.

Partial nephrectomy: The tumor and part of the kidney tissue that surrounds it is surgically removed. This type of surgery is done if the other kidney is not 100 percent healthy, or has already been surgically removed.

Radical nephrectomy: The whole kidney, nearby adrenal gland and lymph nodes, as well as other surrounding tissue are surgically removed.

During the procedure, the surgeon may check both kidneys, as well as the abdominal cavity. Samples may be taken for testing.

Other options

Other options include:

Kidney transplant: If both kidneys need to be taken out, dialysis will be needed until a transplant can be carried out.

Chemotherapy: The tumor cells are examined to determine whether they are aggressive or susceptible to chemotherapy, the use of medication to kill cancer cells. Cytotoxic medication prevents cancer cells from dividing and growing.

Chemotherapy targets unwanted cancer cells, but it can also affect healthy cells, and side effects may result.

These include:

• hair loss
• loss of appetite
• low white blood cell count
• nausea
• vomiting

Once the treatment finishes, side effects usually go away.

High-dose chemotherapy can destroy bone marrow cells. If a high dose is needed, marrow cells may be removed, frozen, and returned to the body intravenously after the treatment.

Radiation therapy: Beams of high-energy X-rays or particles of radiation are used to destroy cancer cells. Radiation therapy works by damaging the DNA inside the tumor cells. This destroys their ability to reproduce.

Radiation therapy usually begins a few days after surgery. Very young patients may be given a sedative so that they are still during a radiotherapy session. The doctor marks the targeted area with a dye, while shielding non-targeted areas of the body.

The following side effects are possible:

Diarrhea: If the abdomen is targeted, symptoms may occur a few days after starting treatment. As treatment progresses, symptoms may get worse, but they usually disappear few weeks after completing the course.

Fatigue: This is the most common symptom.

Nausea: This may occur at any time during treatment or for a short time after. It is important to tell the doctor because it is easily treatable with medication.

Skin irritation: Areas targeted by the radiation beam may become red and sore. These areas should be protected from sunlight, cold winds, from scratching and rubbing, and from perfumed soaps.

Staging

Staging is used to assess how far the cancer has grown or spread.

Stage 1: The cancer can usually be completely surgically removed. It is limited to the kidney.

Stage 2: The cancer has reached tissues and structures close to the kidney, such as blood vessels and fat. However, it can still be completely surgically removed.

Stage 3: The cancer has spread further and reached nearby lymph nodes or other parts of the abdomen. Complete surgical removal may not be possible.

Stage 4: The cancer has spread further still to other parts of the body, including perhaps the brain, liver, or lungs.

Stage 5: Both kidneys have cancer cells.

Treatment by stages

Treatments may be given in the following ways, according to the stage of the cancer:

Stages 1 or 2: If the cancer cell type is not aggressive, the kidney, surrounding tissues and some nearby lymph nodes will be surgically removed. This will be followed by chemotherapy. In some cases, stage 2 may also need radiation therapy.

Stages 3 or 4: If the cancer has spread into the abdomen, removing it might damage major blood vessels or other key structures. In this case, a combination therapy of surgery, radiation, and chemotherapy will be used. Chemotherapy may be used before surgery to shrink the tumor.

Stage 5: If both kidneys have tumor cells, part of the cancer from each kidney will be surgically removed, while nearby lymph nodes will be examined to determine whether they contain cancer cells. After this, the patient will receive chemotherapy to shrink the remaining tumor. Later, more of the tumor is surgically removed. The surgeon will try to spare as much good kidney tissue as possible. This may be followed by more radiation therapy and chemotherapy.

Causes

The exact cause of a Wilms' tumor is unknown, but it probably starts before birth, when some kidney cells do not develop properly. The abnormal cells multiply in their primitive state and become a tumor, which is usually detectable at the age of 3 to 4 years.

Genetic factors: Genes that control cell growth mutate, or change, allowing cells to divide and grow out of control. Two genes have been studied: Wilms Tumor 1 or 2 (WT1 or WT2). There may also be mutations in other chromosomes.

Family history: Wilms tumors may stem from a genetic defect that is passed on by a parent, but most are not inherited. In fewer than 2 percent of cases will a close relative be affected.

Most Wilms tumors occur by chance. They are sporadic, resulting from genetic mutations that affect cell growth in the kidney. These changes usually start after birth.

Co-occurring conditions

WAGR syndrome: In a small number of cases a tumor appears alongside some other genetic conditions.

WAGR stands for four conditions:

• Wilms' tumor
• aniridia, being born with no iris, or colored part of the eye
• genitourinary malformations
• delayed cognitive development

WAGR happens when the WT1 gene is lost or deleted on chromosome 11. WT1 is a tumor suppressor gene. This means is holds back, or suppresses, the growth of tumors and controls cell growth.

A person with WAGR syndrome has a 45 to 60 percent chance of developing Wilm's tumor.

Denys-Drash syndrome (DDS): This is a very rare disorder that causes kidney failure before the age of 3 years. There is abnormal development of the sexual organs. There is a high risk of developing some other types of cancer, apart from Wilms' tumor. It is also caused by inactive or lost WT1.

Beckwith-Wiedemann syndrome: This is an overgrowth disorder with a wide range of symptoms. Weight is significantly higher than normal at birth, and the infant has a large tongue, enlarged organs (especially the liver), overgrowth of one side of the body, low blood sugar in the newborn period, ear creases, and ear pits. The body grows asymmetrically.

It is thought to result from an overactive oncogene copy on chromosome 11 (IGF2). Oncogenes regulate cell growth. If something goes wrong, cell growth may get out of control.

There is a higher risk of developing Wilms' tumor and also hepatoblastoma, neuroblastoma, adrenocortical cancer, and rhabdomyosarcoma.

Other factors

Some other factors make a Wilm's tumor more likely.

Gender: Females have a slightly higher risk of developing Wilms' tumor than males.

Ethnic origin: People of black African ancestry have a slightly higher probability of developing Wilms' tumors. In the United States, Asian-Americans have the lowest risk.

Cryptorchidism: If one or both testicles fail to descend into the scrotum, there may be a higher risk of developing Wilms' tumor.

Hypospadias: Males born with the urethra not located where it should be, at the tip of the penis, have a higher risk of developing Wilms' tumor.

Diagnosis

The doctor will ask about the signs and symptoms, check the child's medical history and details on the pregnancy, and carry out a physical examination.

The following tests can help diagnose a Wilms' tumor:

Blood test: This cannot diagnose a Wilms' tumor, but it can help provide information about the individual's general state of health and the condition of the liver and kidneys.

Urine test: This can assess for sugar, protein, blood, and bacteria.

Abdominal ultrasound scan: This gives an inside view of soft tissues and body cavities and provides an outline of the kidneys and any tumor. It can detect problems in the renal or other veins in the abdomen. Both kidneys will be checked.

Other imaging techniques that may be used include a CT scan or an MRI.

A chest X-ray can show whether the cancer has spread, or metastasized, into the lungs.

In a biopsy, a small piece of the tumor is taken out and examined under a microscope.

Outlook

A Wilm's tumor can be favorable or unfavorable. If it is described as anaplastic, it is unfavorable and more difficult to treat and cure. Anaplasia is when the nuclei of the cells is large and distorted.

Apart from this, other factors that can affect the outlook include:

• the stage of the cancer
• the size of the primary tumor
• the age and general health of the person at diagnosis
• response to therapy and whether the tumor can be removed with surgery
• how well the individual tolerates specific medications, procedures or therapies
• whether there are any underlying genetic changes

Prompt and aggressive therapy is likely to provide the best outcome. Follow-up care is also essential.

For those aged under 15 years at the time of diagnosis, the chance of surviving 5 years or more was 88 percent by 2010, compared with 74 percent in 1975.

According to the American Cancer Society, the chance of surviving at least 4 years is:

For diagnosis at stage 1: 83 percent for an anaplastic tumor and 99 percent for a favorable histology

For diagnosis at stage 5: 55 percent for an anaplastic tumor and 87 percent for a favorable histology

Clinical trials

Clinical trials can be an option if a condition does not respond to existing treatments. Anyone who is interested in finding out about clinical trials can find out more here.