Wilms Tumor (Childhood Kidney Cancer), from the CureRays guide library.

Wilms tumor is the most common kidney cancer in children; it responds very well to surgery, chemotherapy, and radiation, and most children are cured.

What it is.

Wilms tumor, also called nephroblastoma, is the most common kidney cancer in children, usually found in toddlers and young children around ages 3 to 4. It develops from kidney cells that did not fully mature before birth. The most common sign is a smooth, firm swelling or lump in a child's belly, often noticed by a parent during a bath or by a doctor at a check-up; some children also have belly pain, blood in the urine, fever, or high blood pressure. Most Wilms tumors affect only one kidney, but occasionally both kidneys are involved. A small number of children have it as part of an inherited syndrome, so the care team may recommend genetic evaluation. The encouraging news is that Wilms tumor is one of the great success stories of childhood cancer care: it responds very well to a combination of surgery, chemotherapy, and, when needed, radiation. The large majority of children — including many with advanced disease — are cured. Treatment is delivered by a specialized children's cancer team that also focuses on protecting long-term health and growth.

How radiation treats it.

Radiation uses focused high-energy beams to damage the DNA inside cancer cells so they can no longer grow and divide. Wilms tumor is quite sensitive to radiation, so it can be very effective when it is needed. Not every child requires radiation — it is added mainly for higher-stage tumors, for the more aggressive (anaplastic) type, or to treat sites of spread such as the lungs. Because the patients are young children whose bodies are still growing, the care team plans radiation with great care to protect the spine, the remaining kidney, the liver, and other organs, sometimes using proton therapy to reduce the dose to healthy tissue. Treatments are quick and painless, given over a small number of short daily sessions, and young children may have gentle sedation to help them stay still. Side effects are watched closely and managed by the children's cancer team, with special attention to long-term growth and health since the great majority of these children grow up cured.

The ways we can treat it.

Flank (tumor bed) radiation. Targeted radiation to the area where the tumor was removed treats any cancer cells left behind, used for higher-stage disease and shaped to protect the growing spine and organs.

Whole-lung radiation. When the cancer has spread to the lungs, gentle radiation to both lungs helps clear disease alongside chemotherapy, and many children are still cured.

Proton therapy. In children, proton beams can deliver radiation to the target while reducing dose to growing bones and nearby organs, lowering the risk of long-term side effects.

Questions we hear often.

Can Wilms tumor be cured? Yes. Wilms tumor is one of the most curable childhood cancers. With the combination of surgery, chemotherapy, and radiation when needed, the large majority of children — including many with advanced disease — are cured and go on to live full lives.

Does my child need radiation? Not always. Many children with early-stage, favorable tumors are cured with surgery and chemotherapy alone. Radiation is added mainly for higher-stage disease, the more aggressive tumor type, or when the cancer has spread. Your child's team will explain exactly what is needed.

Will my child have long-term problems? Most children grow up healthy. Because treatment happens during growth, the team follows children for years to protect kidney function, growth, and overall health, and uses techniques like carefully shaped or proton radiation to reduce long-term effects.

This guide is informational only. It is not medical advice — please confirm anything here with your care team.