What is a Wilms Tumor?
Wilms tumor, also called nephroblastoma, is a malignant (cancerous) tumor that originates in the cells of the kidney. It is the most common type of kidney cancer in childhood, affecting males and females equally and accounting for about 7 percent of all pediatric cancers.
Approximately 500 children in the United States are diagnosed with this tumor each year. Although the disease can occur at any age between infancy and 15 years, it is often detected in early childhood. The tumor can be very large and it may metastasize (spread) to other body tissues. The most common site of spread is the lungs, but lesions may also occur in the other kidney, the brain, and/or bones. In approximately 5 percent to 10 percent of children with Wilms tumor, both kidneys are involved.
Treatment strategies depend on a number of factors, including the stage of the disease and how aggressive the tumor appears under the microscope. However, surgical removal of the tumor is the cornerstone of therapy. Collaborative treatment strategies that involve pediatric surgeons, pediatric oncologists (cancer specialists), and radiation oncologists have resulted in treatments that cure the majority of patients diagnosed with Wilms tumor, although certain types of this cancer remain difficult to treat.
Cincinnati Children's Hospital Medical Center participates in the Children's Oncology Group, which is a multicenter research group of children's hospitals across the country. We follow the treatment protocols and guidelines that decades of research by such study groups have shown to be the most effective. New methods are continually being discovered to improve treatment and decrease side effects.
Wilms Tumor Causes
Most cases of Wilms tumor are sporadic (occur by chance) and are the result of genetic mutations that occur after birth in kidney cells, causing rapid and uncontrolled cell growth. However, in some cases, patients are born with genetic mutations in all cells in the body, and these patients are at risk for other medical problems as well.
For example, a small percentage of Wilms tumor patients have one of following three genetic syndromes:
- WAGR syndrome -- "WAGR" stands for the four diseases present in this syndrome, including Wilms tumor, aniridia (absence of the iris, which is the colored part of the eye), genitourinary malformations, and mental retardation. This is caused by loss or inactivation of a tumor suppressor gene called WT1. Tumor suppressor genes usually suppress the growth of tumors and control cell growth. When altered, cell growth is no longer controlled, and tumors may form and continue to grow.
- Denys-Drash syndrome -- This syndrome is characterized by kidney failure, genitourinary malformations and tumors of the ovaries or testes. This is also caused by loss or inactivation of the tumor suppressor gene WT1.
- Beckwith-Wiedemann syndrome -- This syndrome is characterized by large birth weight and an enlarged liver, spleen, and tongue. Other characteristics include low blood sugar in neonatal period, malformations around the ear, asymmetric growth of the body, abdominal wall defects near the navel (called omphalocele), and tumors of the liver and adrenal glands. The syndrome is thought to be caused by an overactive oncogene called IGF2. Oncogenes control cell growth; if mutated, uncontrolled cell growth may result.
Wilms Tumor Symptoms
Most children (60 percent) present with a non-tender mass or lump that is felt or seen in the abdomen. It is important not to apply pressure to this area. Careful bathing and handling of the child is necessary, since rupture of the tumor can lead to the spread of cancer cells within the abdominal cavity.
A wide range of other symptoms may also occur. These include swelling of the abdomen, veins that appear distended or large across the abdomen, pain in the abdomen from pressure on other organs near the tumor, blood in the urine (hematuria), decreased appetite, weakness or fatigue, fever and high blood pressure (hypertension).
Wilms Tumor Diagnosis
In addition to a complete medical history and thorough physical examination, diagnostic procedures may include:
- Abdominal ultrasound -- This is a technique that uses high frequency sound waves and a computer to create images of blood vessels, tissues and organs. It provides an outline of the kidneys and the tumor, and can determine if there are problems in the renal or other major veins in the abdomen. It can also determine if there are any lesions or tumors in the opposite kidney.
- Computerized tomography (CT) scan -- This procedure uses a combination of X-rays and computer technology to produce horizontal and vertical cross-sectional images of the body that are more detailed than what can be seen in X-rays. A CT scan shows images of any part of the body, including the bones, muscles, fat, and organs.
- Magnetic resonance imaging (MRI) -- This procedure uses a combination of large magnets, radiofrequencies, and a computer to produce detailed images of organs and structures within the body. It can determine if there are metastases, if there is enlargement of lymph nodes, and/or if any other organs are involved. Wilms tumors can compress other organs in the area, thus affecting their function. This test is not always necessary, but may be helpful in some situations to plan surgery.
- Chest X-ray -- This uses radioactivity to produce images of internal tissues, bones, and organs onto film. A chest X-ray can determine if the tumor has metastasized (spread) to the lungs.
- Blood and urine tests -- These are done to evaluate kidney and liver function.
- Nephrectomy (surgical removal of the tumor and kidney) -- Surgery is usually necessary to determine the extent of the disease and provide tissue to make a definitive diagnosis. Lymph nodes are also sampled so that the disease can be staged and an appropriate course of chemotherapy can be prescribed.
Wilms Tumor Treatment
Treatment strategies for Wilms tumor depend upon the stage of the disease, which refers to the extent and progression of the tumor and the appearance of the tumor under the microscope. For example, some tumors have a particularly aggressive microscopic appearance, and require more intensive treatment.
- If there is no evidence of tumor involving the opposite kidney, then the involved kidney is surgically removed along with the tumor. In addition, lymph nodes near the tumor are removed and evaluated for any evidence of cancer involvement.
- Chemotherapy is currently recommended for all patients, regardless of the extent of tumor involvement or results of the surgery. The intent of treatment with chemotherapy is to eliminate any remaining microscopic tumor cells following surgery, in order to decrease the chance of the cancer coming back. The type and intensity of the chemotherapy is dependent on the stage of the disease and how aggressive the tumor appears under the microscope.
- Radiation therapy is used in selected patients with more advanced disease to shrink the remaining tumor or to treat metastasis and/or recurrent disease.
- Medications are used to control pain, hypertension, nausea, and infections.
As with all malignancies, continuous follow-up care is absolutely essential. This is done to determine the child's response to treatment, detect possible recurrent disease, evaluate function of the remaining kidney, and to manage any late effects of treatment which may arise.
Cincinnati Children's is an international referral center for the treatment of children and young adults with high-risk and relapsed cancers. Our faculty leads national efforts in the development of new targeted therapies, immunological approaches, and stem cell transplantation.