Disease Information

Solid Tumor: Wilms Tumor

Alternate Names: nephroblastoma

Definition

• Wilms tumor is a solid tumor of the kidney that arises from immature kidney cells.
• It is the fourth most common type of cancer in children.
• Approximately 460 new cases of Wilms tumor are diagnosed each year in the United States, and 1 in 8,000-10,000 children are affected.
• Average age at diagnosis is about three years, although older children and even adults are occasionally diagnosed with Wilms tumor.
• Girls and boys are equally affected.

Other kidney cancers that are much less common than Wilms tumor occasionally arise in children. These tumors include clear cell sarcoma of the kidney, rhabdoid tumor of the kidney, renal cell carcinoma, undifferentiated sarcoma, and congenital mesoblastic nephroma. These tumors behave differently from Wilms tumor and require distinct treatments.

Influencing Factors

• Most children affected with Wilms tumor have no clear underlying cause for their disease.
• Several small studies have suggested that certain environmental factors may be associated with a higher risk of Wilms tumor, but the results were conflicting. A nationwide research study is underway to clarify whether exposure to drugs, chemicals, and infectious agents is associated with Wilms tumor.  

A few children are born with a genetic predisposition to Wilms tumor, which may reveal itself in several ways:

• Congenital abnormalities:  It is well documented that certain syndromes, or clusters of inborn abnormalities, are associated with Wilms tumor. The syndromes associated with the greatest risk of Wilms tumor are the WAGR syndrome (Wilms tumor-aniridia-genitourinary malformation-retardation), the Denys-Drash Syndrome, and the Beckwith-Wiedemann Syndrome.
• Familial Wilms tumor:  Approximately 1.5 percent of children with Wilms tumor have a relative who was also affected with Wilms tumor.
• Bilateral Wilms tumor: About 5-10 percent of patients with Wilms tumor have multiple tumors in one or both kidneys. Having multiple tumors does not indicate tumor spread. Rather, each tumor develops on its own, which reflects an underlying genetic predisposition to Wilms tumor.

Treatment Strategies

• Treatment involves a combination of therapies that include surgery, chemotherapy, and, in advanced cases, radiation therapy. With this approach, cure rates are now 85-90 percent.
• Nearly all patients undergo surgery as the primary method to remove the tumor. In North America, most patients have the tumor removed at the time of diagnosis. In Europe, most patients receive a few weeks of chemotherapy and then have the tumor removed. Both approaches produce high rates of treatment success.
• Tumors that are difficult to remove or bilateral tumors are almost always treated with chemotherapy first to make subsequent surgery easier.

There are two major categories of Wilms tumor: favorable (95 percent) and anaplastic (5 percent).

• For those with favorable Wilms tumor, the most widely used chemotherapy drugs are vincristine and dactinomycin. Patients with extensive disease or tumor that has spread to distant sites also receive the drug doxorubicin.
• Patients with anaplastic Wilms tumor require more intensive chemotherapy, which typically includes the agents vincristine, doxorubicin, cyclophosphamide, ifosfamide, etoposide, and carboplatin. In addition to chemotherapy, patients with extensive disease receive radiation therapy to the affected sites.
• For Wilms tumor that has returned after primary treatment (relapsed), treatment depends on the extent of disease and prior treatment. A St. Jude trial found that topotecan is active in patients with relapsed favorable Wilms tumor.

Current Research

• Current studies are attempting to limit therapy, and its associated side effects, for patients with a low risk of tumor recurrence while increasing therapy for patients with a high risk of tumor recurrence.
• Laboratory studies are trying to identify tumors that are more likely to be resistant to therapy.
• Investigators are conducting research to determine whether occupational or environmental factors contribute to the development of Wilms tumor.

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