Wilms Tumor

Wilms tumor (also called nephroblastoma) is a cancerous tumor in the cells of the kidney. Fortunately, with the right treatment, it is highly treatable.

It is the most common type of renal (kidney) cancer in children, accounting for about 6 percent of all childhood cancers. About 500 children in the U.S. are diagnosed with a Wilms tumor each year. It can occur at any age between infancy and age 15, but is most common in children age 5 or younger. Adults rarely have Wilms tumor.

The tumor can spread outside the kidney, most often to the abdominal lymph nodes and lungs. With prompt and aggressive treatment, Wilms tumor is successfully treated in the majority of children. Multidisciplinary approaches, including a combination of surgery and/or chemotherapy and/or radiation therapy, can be used.

The most common symptom of Wilms tumor is the sudden appearance of a solid mass in the abdomen. Though each child may experience symptoms differently, other symptoms may include:

• Swelling of the abdomen
• Blood in the urine
• Abdominal pain
• Decreased appetite
• Weakness or tiredness
• Fever
• High blood pressure
• Constipation

Keep in mind that Wilms tumor symptoms may resemble other more common conditions or medical problems. Always consult your child's physician for a diagnosis.

Most cases of Wilms tumor occur with no family history of the disease or other known cause. In a small number of cases, children are born with a genetic predisposition to develop Wilms Tumor. These children have rare genetic syndromes such as:

• Hemihypertrophy
• WAGR syndrome
• Denys-Drash syndrome
• Beckwith-Wiedemann syndrome

The first step in treating your child is forming an accurate and complete diagnosis. Your child’s physician may recommend a number of different tests to determine the cause of the symptoms. In addition to a complete medical history and physical examination, your child’s doctor may order one or more of the following:

• Abdominal ultrasound
• X-ray
• Computed tomography (CT)
• Magnetic resonance imaging (MRI)
• Blood and urine tests
• Biopsy
• Surgery

After we complete all necessary tests, our experts meet to review and discuss what they have learned about your child's condition. Then we will meet with you and your family to discuss the results and outline the best treatment options.

Your child’s physician will determine a specific course of treatment based on several factors, including:

• Your child's age, overall health, and medical history
• Type, location, and size of the tumor
• Extent of the disease (stage)
• Your child's tolerance for specific medications, procedures, or therapies
• How your child's doctors expect the disease to progress
• Genetic characteristics of the tumor

The first step in Wilms tumor treatment is surgery to remove the tumor. The most common operation is a radical nephrectomy, which removes the whole kidney, the tissue around the kidney, the ureter (the tube that drains urine from the kidney to the bladder), and the adrenal gland (which sits on top of the kidney). This operation is performed if the tumor has occurred in only one kidney. Some cases of low-stage Wilms tumor can be treated with surgery alone.

If your child has bilateral Wilms tumor (tumor in both kidneys) or has a known predisposition to kidney cancer, your child’s physician may recommend a partial nephrectomy or kidney-sparing surgery that aims to remove the tumor while leaving the maximum amount of healthy kidney tissue.

In rare cases — when the tumor is very large — your child’s doctor may recommend chemotherapy to try to shrink the tumor before surgery. In some cases, a biopsy may be the best first surgical procedure for your child, to establish the diagnosis before treatment.

Surgical procedures for Wilms tumor — especially bilateral tumors — should be performed in specialized centers where experienced surgeons, working in the most technologically advanced settings, can provide the most appropriate kidney surgery. Surgeons at Dana-Farber/Boston Children’s have extensive, specialized experience in treating Wilms tumor.

Surgery is usually followed by chemotherapy and sometimes radiation therapy. The type of chemotherapy and need for radiation are determined by tumor stage (extent of spread of the tumor) and tumor type. Radiation therapy may be indicated for some tumors, including any that have spread to the lymph nodes in the abdomen or the lungs.

In very rare cases, a stem cell transplant, involving a transplant of your child’s own stem cells, may be used. This allows your child’s physician to give high-intensity chemotherapy in difficult-to-treat cases of Wilms tumor. Stem cell transplantation and the treatment needed to manage its effects are complex and involve some risk. Your physician will give you more detailed information on what to expect.

Treating other kidney tumors

Malignant rhabdoid tumor of the kidney was once considered a subset of Wilms tumor but is now classified as a separate tumor type in its own right. Other types of kidney tumors include renal cell carcinoma, clear cell sarcoma of the kidney, cystic nephroma, and congenital mesoblastic nephroma.

As with any cancer, prognosis and long-term survival can vary greatly from child to child depending primarily on the stage of the disease and the tumor cells' appearance under a microscope. Prompt medical attention, aggressive therapy, and continued follow-up care are important for the best possible prognosis.

With prompt, aggressive treatment, most children with Wilms tumor are successfully treated and experience relatively few side effects. More aggressive tumors that have spread significantly may be harder to cure. Should a tumor come back after treatment, your doctor may recommend additional surgery, chemotherapy, and/or radiation therapy.

The goal of treatment is both to cure the cancer and minimize the long-term effects of therapy. Children, however, are at some risk of late-effects of the cancer and its treatment, including high blood pressure, heart and lung problems after chemotherapy or radiation therapy, and slowed or decreased growth and development. Reduced kidney function may appear primarily in children with tumors in both kidneys (bilateral involvement) or with a predisposition syndrome that causes kidney abnormalities (nephritis) distinct from those related to the tumor or treatment.

Factors that influence the outlook for a child with Wilms tumor include:

• Extent of the disease
• The histology of the tumor (what it looks like under the microscope)
• Genetic changes in the tumor
• Age and overall health of the child at diagnosis
• Size of the primary tumor
• Response to therapy
• Your child's tolerance of specific medications, procedures, or therapies

Researchers at Dana-Farber/Boston Children’s Kidney Tumor Program conduct laboratory and clinical research designed to improve understanding and treatment of pediatric kidney tumors. We also offer clinical trials through the Children’s Oncology Group (COG).

Identifying the best treatment for Wilms tumor

Major advancements have occurred in the treatment of Wilms tumor over the last three decades, primarily because of studies by the National Wilms Tumor Study Group and Children's Oncology Group, in which Dana-Farber/Boston Children’s physicians have played key roles. These studies have rigorously compared treatment regimens (treatment plans) and helped define the optimal treatment for each stage and type of Wilms tumor. In one large study, it was shown for low-stage Wilms tumor that briefer courses of therapy were safer and as effective as longer courses. A recent COG study initiated by Dana-Farber/Boston Children’s doctors, including Robert Shamberger, MD, and Elizabeth Mullen, MD, FAAP, demonstrated that young children (less than 2 years of age) with small tumors can be treated safely with surgery only, without the need for chemotherapy or radiation. This study also offered adjustments of therapy for children with Stage I, II, and III tumors based on specific genetic findings. This study is the first study in childhood renal tumors to base therapy on the biology of the individual child’s tumor. Elizabeth Mullen, MD, FAAP, is the vice-chair of this study.

Renal tumor biology and risk stratification

Elizabeth Mullen, MD, FAAP, is the Protocol Chair for the COG Renal Tumor Biology and Risk Stratification Protocol (AREN03B2). This has been open since 2006, remains open to accrual, and currently has enrolled over 4,800 patients. This study involves real-time, coordinated review of Wilms tumor diagnoses by multiple specialists to determine the most accurate staging and risk stratification. Through this study, researchers have learned that many cases of Wilms tumor are initially misdiagnosed or not accurately staged. Through accurate diagnosis and staging, however, children can receive the best possible treatment regimen.

Risk-stratifying treatment of children with bilateral tumors

The traditional treatment for pediatric kidney tumors is a two-step process: Surgeons remove as much of the tumor as possible, then oncologists use chemotherapy to kill remaining cancerous cells. If the tumor is bilateral (appearing in both kidneys), chemotherapy is sometimes also used before surgery to reduce the size of the tumor so as to save the maximum amount of healthy kidney tissue. Our researchers are investigating the use of continuous pathological review throughout treatment to evaluate the best therapeutic approach for bilateral pediatric kidney tumors.

Searching for markers

Researchers are conducting studies to better understand how to diagnose and treat renal tumors. For example, our researchers are investigating whether kidney tumors emit markers in a child’s urine. If discovered, these markers could be used to screen for early recurrence of relapsed cancers. They may also help clinicians screen types of tumors up front, so treatments are personalized to the exact make-up of a child’s tumor. Dana-Farber/Boston Children’s is also involved in one of the country’s most comprehensive precision cancer medicine initiatives, called Profile. Ultimately, this important research project will result in a database of genetic changes in all types of cancer, including Wilms tumor. This research is advancing scientists’ understanding of the genetic causes of cancer and how that information may ultimately lead to improved treatment.

For many children with rare or hard-to-treat conditions, clinical trials provide new options.