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 fifteen. 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 nephroblastoma. 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 Wilm’s tumor include:
Sotos syndrome (cerebral gigantism)
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. Girls are at slightly greater risk than boys, and peak incidence rates occur before five years of age. Family history of the disease has been linked to one to two percent of all cases.
Often no symptoms are apparent. The first indication of the disease is often a noticeable abdominal mass. If other symptoms are present, the child may experience fever, stomach pain, hematuria (blood in the urine) and hypertension (high blood pressure).
Diagnosis of Wilms’ Tumor
Diagnosis is similar to 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 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
NWTS staging determines how advanced the disease is (NWTS stands for National Wilms’ Tumor Study Group). The accompanying box explains the different stages of the disease. 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. 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 ninety percent if the cancer is confined to the kidney. Even if the disease has metastasized, survival rates average seventy percent.
Wilms’ tumor is a rare childhood cancer. Because of this, 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.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 5 percent of cases.