AUA Summit - What is Kidney Cancer in Children?


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What is Kidney Cancer in Children?

Kidney (renal) tumors are very rare in children. Still, the three most common renal tumors found in children are:

  • Wilms' tumor (about 6 to 7 of every 100 childhood cancers in the U.S.)
  • Congenital Mesoblastic Nephroma (mostly found during the first 3 months of life)
  • Renal Cell Cancer in the renal tubules (mostly found in older children)

Fortunately, renal tumors found in children are often very treatable and curable.

What are the Types of Kidney Cancer in Children?

Wilms' Tumor (also called nephroblastoma)

This is the most common form of kidney cancer in children, affecting 450 to 500 kids per year. Wilms' tumor makes-up about 5% of childhood cancer cases in the U.S. It occurs a little more often in girls, and is most often found in children younger than five.

Renal Cell Cancer (RCC) (also called renal adenocarcinoma or hypernephroma)

This cancer causes changes in the cells of the renal tubules. RCC is more common than Wilms' tumor after the age of 10 years. But overall, it is less common than Wilms' tumor. This cancer spreads easily, most often to the lungs and other organs. About 1/3 of cases are found after the cancer has spread.

Congenital Mesoblastic Nephroma

This cancer is mostly found during the first 3 months of life. There are some children who have an unusual type that can spread outside the kidney. This is more common if the disease is found after the age of 3 months. The good news is that surgical removal of the affected kidney provides an excellent outcome. Radiation and/or chemotherapy are not needed in most infants after complete removal of the tumor.

What can be Expected under Normal Conditions?

Most people have 2 kidneys. The kidneys are found toward the lower back, with one on either side. The kidneys make urine, which drains through thin tubes (called ureters) into the bladder.

The main work of the kidney is to clean our blood and remove waste (urine). The kidney has other vital roles as well. It serves as our body's filter to control electrolytes, fluid balance, blood pressure and pH balance.

The kidneys are strong organs. In most cases, a small amount of damage won't cause many problems. But, major damage may need long-term treatment, like dialysis.


The exact cause of kidney cancer is not known. Wilms’ tumor has been linked to some birth defects.

Wilms’ tumor also has a greater chance of showing up in brothers and sisters. This suggests that it can be passed down in families.

There has been a lot of interest in the genetics of how renal tumors grow in children. Some specific changes in chromosomes have been linked to a greater risk for Wilms’ tumor and tumor growth. Experts hope that this might shed some light on how to treat this disease.


A lump is the first sign. A lump in the child's belly may be felt during bathing, dressing or other daily activities. Or, it may be found during a routine exam by the pediatrician.

Other signs could be:

  • Blood in the urine
  • Pain in the belly
  • Fever
  • Lack of appetite
  • Weight loss
  • Trouble with stools
  • High blood pressure


If a child has a mass or lump in his/her belly, a doctor will do an exam and order tests:

  • Ultrasound: to show if the mass started growing in the kidney or somewhere else, and if it is solid.
  • CT or MRI: to see the size of the mass, and if it has spread.

For Wilms' tumor it is important to find out:

  • If it has grown into the vascular system
  • If it is in both kidneys
    • About 5 of every 100 patients have Wilms' tumor on both sides. If this is found early, the treatment plan will be adjusted
  • If the kidney without the tumor is working well

Where Renal Cancer Spread?

  • Lungs: This is the most common site for renal cancer cells outside the kidney. A chest X-ray will show most tumors. Smaller tumors can only be seen with a CT scan.
  • Bones: Rare tumor types, like clear cell sarcoma and rhabdoid tumor of the kidney, can spread to the bones. This is also true for RCC. Bone scans are done in some patients.
  • Brain: Rhabdoid tumor of the kidney can spread to the brain. So MRI of the brain is done in some patients.


After the type of kidney cancer cells are defined, the cells are "staged" and "graded". The stage of a solid tumor refers to its size or extent and whether or not it has spread to other organs and tissues. The grade of a tumor is an indication of how quickly it is likely to grow and spread. In general, low-grade tumors grow slowly and higher-grade tumors grow more rapidly.

A carefully diagnosed grade and stage will help your health care team find the best treatment.

Renal cancer cells are also defined in other ways.

Wilms' tumors are split into 2 types:

  • Favorable
  • Unfavorable

"Unfavorable" types do not respond well to standard chemotherapy. RCC that occurs later in childhood does not respond well to chemotherapy, for example. This is important information for planning treatment.

Also important for planning treatment, is learning exactly where the cancer cells are found. If the tumor is only in the kidney, then it can be removed fully with surgery. This is vital for those who have unfavorable microscopic cancer cells.

General stages for kidney cancer are:

    • Stage I: Tumor only in the kidney
    • Stage II: Tumor in the kidney with some local spread, tumor in kidney vein
    • Stage III: Local lymph nodes show kidney cancer
    • Stage IV: Kidney cancer spread to lung, liver, bone or brain
  • Stage V: Bilateral tumor – tumors on both kidneys


The main treatment for all renal tumors in children is surgery to remove the tumor. For most patients, a surgery called radical nephrectomy is done.

Radical Nephrectomy

In this surgery, the tumor and whole kidney are removed. The doctor will look at the nearby lymph nodes and the liver to see if cancer has spread. It is critical to know if the tumor is only in the kidneys.

Radical Nephrectomy for Wilms' Tumor

Wilms' tumors are very soft, and they can burst before and during surgery. If they burst, the stage of the disease can change and add to the risk of the tumor coming back.

In patients with tumors in both kidneys, neither kidney should be removed at the first surgery. To start, a biopsy of the tumor is done to help pinpoint the tumor type.

If appropriate, chemotherapy (drugs for cancer) is used. The goal is to first shrink the tumors. After chemotherapy, surgery is considered. At this point, the goal of surgery is to remove the tumor, and save as much of the kidney as possible. This plan works better for the favorable type of Wilms' tumor.

Radical Nephrectomy for RCC

RCC is also mainly treated with surgery. It is not a curable cancer, but surgery can remove the tumor(s). The cases with tumors that are only in the kidney have the best results.

Additional Treatment

After surgery, most patients with Wilms' tumor receive chemotherapy and some receive radiation therapy.

Chemotherapy (chemo)

The drugs used most often are dactinomycin and vincristine. These drugs have been used for 30 years with very good success.

  • With surgery alone, the survival rate is only 25 out of 100.
  • With chemotherapy, the survival rate is nearly 90 of every 100.

Each child will receive a dose of these drugs based on their personal health. Generally, children who have the whole tumor removed get chemo for 6 months. If the tumor is still present or it has spread, a child will be given a different type of drug, such as doxorubicin.

Radiation Therapy

Radiation therapy uses special x-rays to shrink tumors. This can be used depending on where the tumor has spread. With the other treatments, radiation can improve survival. But, there is some risk of side effects.

Radiation does not seem to work on unfavorable tumor types. Research is being done to find better ways to treat these tumors.

After Treatment

The chance that a child will be cured depends on the type, stage and location of the tumor.

For Wilms' Tumor

This type of tumor has a high cure rate with treatment. Now, more than 90 of every 100 children with favorable tumors survive. But there can be complications. The tumor can spread to the lungs, bone or brain. Removal of a bilateral tumor may harm the way kidneys function. Ongoing follow-up care will be important.


The outcome varies based on how far the tumor has spread. This is a very difficult cancer to treat. The 5-year survival rate is around 50-75% if the tumor is found early. If it has spread to the lymph nodes, the 5-year survival drops to 10-15%.


Ideally, tumors that return are caught quickly and can be more easily managed. A conservative approach to surgery will be used to protect the kidney.

Children with very aggressive cancers are harder to treat. Wilms' tumors may come back in several sites, including:

  • Lung
  • Liver
  • Local surgical area
  • Opposite kidney (occurs later)

The timing for when a returning tumor is found is important. If the disease comes back early in kids on chemotherapy, it is very hard to manage. If cancer is found in the abdomen after radiation, it also means the cancer is aggressive.

There are lesions (sores) in the kidney that are known to show up before Wilms' tumor. These lesions must be watched very closely. Regular imaging will be done to try to manage new tumors before they spread.

Treatment Side Effects

All cancer treatment has side effects. Some things can be managed well, like nausea. Other side effects can't be avoided. As a child's body develops, they may experience long term affects from cancer drugs.

Musculoskeletal Problems

Fortunately, modern radiation aims to protect children's bones. The amount of radiation therapy given to children with Wilms' tumor has decreased. Less often, children experience problems with the way their spine grows. Physical therapy is helpful to strengthen muscles around the spine.

Other Cancers

Additional cancer is a major concern for children who have been treated for kidney cancer. The bone, breast and thyroid are carefully watched. Children who had radiation therapy or were treated with doxorubicin are at higher risk.

Children enrolled in clinical trials for treatment are followed closely throughout their life. Clinical trails are a great way to receive ongoing and careful care. You can ask your doctor if it's possible to enroll in a clinical trail.

Fertility Issues

Some patients who receive radiation in the abdominal area may not reach puberty properly. Ovarian failure and testicular failure have also occurred. This is a concern for some people.

Kidney Function

For children with one remaining kidney, it is important to pay attention to the health of that kidney. Often, the remaining kidney can keep the body healthy. Sometimes, the remaining kidney experiences damage. Dialysis may ultimately be needed.

What Questions Should I Ask My Doctor?

  • What is the stage and grade of this cancer and what does that mean?
  • Has it spread anywhere else?
  • Are other tests needed before we can decide on treatment?
  • What are our treatment options? Which do you recommend and why?
  • What are the chances my child's cancer can be cured?
  • What are the chances that cancer will return after treatment?
  • What does recovery from surgery look like?
  • What risks or side effects should I expect from treatment? For how long?
  • What will we do if the treatment doesn't work?
  • Can you recommend another pediatric oncologist for a second opinion?
  • Is there anything I can do to protect my child from here?
  • How often will we need checkups after treatment?

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