Wilms tumor is a primary cancer of the kidney. It accounts for 5 to 6 percent of all childhood cancers in the United States—approximately 500 children are diagnosed each year. Wilms tumor occurs most commonly in children younger than age 5. Girls have a slightly higher incidence than boys. Blacks and whites have similar incidence rates, but Asians are much less likely to develop Wilms tumor. A small percentage of Wilms tumors are believed to be inherited. In cases where the disease is inherited, there is a higher incidence of bilateral disease (meaning in both kidneys).

Treatment

Choice of treatment depends on histology (i.e., how it looks under a microscope), extent of disease (called stage), size of the tumor, and age of the child.

Surgery

Children diagnosed with Wilms tumor usually have a surgical procedure called a nephrectomy (removal of a kidney) performed before any other therapy is started. Occasionally, if the diagnosis is questionable, a biopsy will be performed prior to the nephrectomy. After biopsy or surgery, the pathologist examines the nuclei of the cancer cells under a microscope. If the nuclei of some of the cells appear larger than normal or irregular in shape, it is called anaplasia. If there is a large amount of anaplasia scattered throughout the tumor, it is called diffuse anaplasia.

Tumor cells that are not anaplastic are called Wilms tumor of favorable histology. Ninety-five percent of children with Wilms tumor have favorable histology. Children with unfavorable histology require more intense treatment.

For the majority of children, the goals of surgery are to remove the tumor, prevent rupture of the tumor capsule, and provide tissue for examination and staging. During surgery, the kidney with the tumor is removed, the other kidney is examined (to diagnose the 5 percent of cases in which both kidneys have tumor cells), and lymph nodes in the region are biopsied.

Chemotherapy

All children diagnosed with Wilms tumor receive chemotherapy. There are several chemotherapy drugs that are effective against this type of cancer. The use of dactinomycin (Cosmegen ^® ) and vincristine (Oncovin ^® ) has dramatically increased survival rates. Children with early stage disease are often treated with just these two drugs. For those who are diagnosed at more advanced stages, doxorubicin (Adriamycin ^® ) and cyclophosphamide (Cytoxan ^® ) may be added. In North America, only those children with bilateral Wilms tumor receive chemotherapy prior to surgery.

Radiation

In the past, all children with Wilms tumor received radiation, some at very high doses. But now, because of the risk of long-term complications from radiation therapy, the decision to use it to treat a child with Wilms is based largely on the stage and histology of the tumor.

Late effects

Some children with stage I or II disease have few or no long-term effects. Children with higher risk disease, or those who relapse and require more intensive treatment, sometimes pay a higher price. The following information briefly outlines some common and uncommon late effects from treatment. Remember that you may develop none, a few, or several of these problems in the months or years after treatment ends.

Growth problems. A child whose trunk is irradiated may have curvature of the spine and soft tissue underdevelopment in the radiated areas (most common in those treated prior to 1970). When lower doses of radiation (1000 to 2500 cGy) are given to all or parts of the spine, up to 40 percent of survivors have reduced sitting heights (measured from the rump to the top of the head). This problem is more common in children who were younger than age 6 and in adolescents going through their growth spurt when irradiated. For more information, see Chapter 17 .

Heart problems. In some patients, heart problems can occur months or years after treatment with anthracyclines (i.e., doxorubicin, idarubicin, or daunorubicin), high-dose cyclophosphamide, or chest radiation. Symptoms include shortness of breath, fatigue, wheezing, anxiety, poor exercise tolerance, rapid heartbeat, and irregular heartbeat. Survivors often have no symptoms, but problems may be found on cardiac tests such as echocardiograms, electrocardiograms (EKGs), and Holter monitors. In a study of Wilms tumor survivors who were treated with doxorubicin in National Wilms’ Tumor Studies 1, 2, 3, and 4 and who did not relapse, more than 4 percent developed heart problems. ⁴ Abdominal radiation can cause damage to major blood vessels, including the aorta and renal vessels. For more information, see Chapter 12 .

Hepatitis C. Infection with the hepatitis C virus can develop in survivors who had blood transfusions prior to July 1992. For more information, see Chapter 15 .

Fertility and pregnancy. Girls who had abdominal radiation can experience ovarian failure. Survivors who do become pregnant have a risk of delivering low birthweight babies, of impaired development of the fetus due to maternal scoliosis (curvature of the spine), or of reduced blood supply from damaged vessels. Offspring are not at risk of developing Wilms if the mother had the non-inherited form in only one kidney. Any young woman who had Wilms tumor should get genetic counseling to fully understand her particular situation, and, if pregnant, should be cared for by an obstetrician who specializes in high-risk pregnancies. This gives the best chance for a full-term pregnancy and a healthy baby. Children fathered by males treated for Wilms are just as healthy as children of fathers with no cancer history. For more information, see Chapter 3 and Chapter 9 .

Newer technologies can sometimes help infertile couples have a baby. Counseling and support for infertile couples allow them to explore their options and address their feelings about infertility.

Digestive problems. A very small number of survivors who were treated with flank or whole abdomen radiation develop chronic gastrointestinal disturbances. For more information, see Chapter 15 .

Second cancers. Second cancers develop in a very small number of Wilms survivors. The most common—bone, breast, thyroid, leukemias, and lymphomas—are usually found in irradiated areas. For more information, see Chapter 19 .