Pediatric Cancer Wilms Tumor

Wilms’ tumor is the most common childhood cancer of the kidney. Also called nephroblastoma or renal embryoma, Wilms’ tumor accounts for 95 percent of pediatric renal cancers occurring before age 15. Treatment methods for the disease differ from those for renal cell carcinoma, the most common adult kidney cancer.

Birth Defects and Other Risk Factors

Certain birth defects raise the odds that childhood cancer of the kidneys will develop. Fifteen percent of cases are linked to birth defects. Children with WAGR syndrome, for instance, have a 33 percent chance of developing Wilms’ tumor.

WAGR stands for Wilms’ tumor, aniridia, genitourinary tract abnormalities and mental retardation. Aniridia is the partial or complete lack of irises in the eyes. Genitourinary abnormalities are defects of the kidneys and/or sexual organs.

Other birth defects that may lead to the development of Wilms’ tumor include:

  • Beckwith-Wiedemann Syndrome: This is a genetic disease characterized by hypoglycemia and hernia.
  • Denys-Drash Syndrome: This syndrome is a disease associated with kidney problems and genital malformation.
  • Perlman Syndrome: This is a disease that causes kidney defects.
  • Sotos Syndrome: This is a syndrome causing cerebral gigantism or an enlarged, abnormally shaped head.
  • Simpson-Golabi-Behmel Syndrome: This is a disease that causes overgrowth and malformation of facial features.
  • Bloom Syndrome: This is a syndrome characterized by growth deficiency and immunodeficiency.

Ethnicity, heredity, age and gender also influence one’s risk:

  • African American children are more susceptible to the disease than children of Caucasian or Asian descent.
  • Family history of the disease has been linked to 1 percent to two percent of all cases.
  • Girls are at slightly greater risk than boys.
  • Peak incidence rates occur before five years of age.

Symptoms

With Wilms’ tumor, there are sometimes no symptoms that are apparent. The first indication of the disease is often a noticeable abdominal mass. If other symptoms are present, they may include:

  • fever
  • hematuria (blood in the urine)
  • hypertension (high blood pressure)
  • stomach pain.

Not all children will experience all of these symptoms but if they occur and are persistent, it’s a good idea to take the child to the doctor as soon as possible.

Diagnosis of Wilms’ Tumor

Diagnosis of Wilms’ tumor is similar to diagnosis of adult renal cell carcinoma. CT scans, ultrasound and other diagnostic tools are used to determine the location and size of the cancer. Bone scans and CT scans are also used to determine if the disease has spread to other organs, most often the lungs, liver or lymph nodes. A biopsy sample is required to make a firm diagnosis.

Treatment

Treatment of Wilms’ tumor often involves the surgical removal of the diseased tissue. Unlike RCC, nephroblastoma responds very well to both chemotherapy and radiation therapy.

Staging, Histology and Prognosis

National Wilms’ Tumor Study Group (NWTS) staging determines how advanced the disease is. Stage I offers the best prognosis.

In addition to NWTS staging, the histology of the cancer cells is also considered. Histology examines the disease at a cellular level. A favorable histology indicates that the diseased cells are mature and resemble healthy kidney cells. An unfavorable histology includes anaplasia, or immature looking cells with deformed, and often larger than normal nuclei, or cell centers. The closer the histology of the cancerous cells is to healthy cells, the better the prognosis.

Overall, the prognosis for Wilms’ tumor is very favorable. The five-year survival rate is 90 percent if the cancer is confined to the kidneys. Even if the disease has metastasized, or spread, survival rates average 70 percent.

NWTS Staging System

  • Stage I: Limited to the kidney and surgically removable; comprises about 41 percent of cases.
  • Stage II: Grown beyond the kidney but still surgically removable; comprises about 23 percent of cases.
  • Stage III: Limited to the abdominal cavity, and not entirely removed during surgery; comprises about 23 percent of cases.
  • Stage IV: Metastasis to distant organs has occurred; comprises about 10 percent of cases.
  • Stage V: Both kidneys affected concurrently; comprises about five percent of cases.

Clinical Trials

Wilms’ tumor is a rare childhood cancer. Therefore clinical trials are often short of participants. Parents and guardians of children with the disease are encouraged to consider clinical trials. Current clinical trials include examinations of prognostic factors and investigations into the role family history may play in the disease.

Resources

Mayo Clinic (2007). Wilms’ Tumor. Retrieved September 4, 2007, from the Mayo Clinic Web site: http://www.mayoclinic.com/health/wilms-tumor/DS00436.

National Cancer Institute (2007). General Information About Wilms Tumor and Other Childhood Kidney Tumors. Retrieved September 4, 2007, from the National Cancer Institute Web site: http://www.cancer.gov/templates/doc.aspx?viewid=54D04049-1965-49D3-A2FF-2E587BEACBCE