Wilms Tumor is a kidney cancer that typically occurs in young children under 9 years of age. In about 10% of patients Wilms Tumor occurs in both kidneys, and in some instances one kidney has a malignant tumor while the other kidney has one or more benign nodules. In rare instances Wilms Tumor is associated with additional abnormalities such as absence of an iris in the eye (aniridia), left versus right-sided limb length differences (hemihypertrophy), or enlargement of the tongue and large birth weight (as in Beckwith-Weidemann syndrome). Wilms Tumor can spread to lymph nodes in the abdomen and to the lung, and rarely to the liver, but does not spread to the bones, bone marrow, or brain.
Signs or symptoms concerning for Wilms Tumor include:
- abdominal swelling
- an abdominal mass
- abdominal pain
- diminished appetite
- blood in the urine
- high blood pressure
Diagnostic Testing and Surgery
After a careful history and physical examination, we typically obtain:
- CT scan of the chest, abdomen, and pelvis, with oral and intravenous contrast
- chest X-ray (as a baseline to assist follow-up)
- ultrasound of the abdomen, to assess major blood vessels for tumor involvement
- urinalysis for blood and protein
- blood tests to measure blood counts and liver and kidney function
- cardiac echo and EKG, as a baseline
- consultation with a surgeon and a radiation oncologist
Wilms Tumor will be seen on CT scan as a large solid mass within the kidney, pushing the normal kidney to the side. The radiologist can usually easily distinguish a solid tumor in this location from benign processes such as cystic disease or infection.
Although Wilms Tumor is by far the most common solid tumor that develops in the kidney in pediatric patients, other tumors that might be present include mesoblastic nephroma (typically in infants), clear cell sarcoma, rhabdoid tumor, and renal cell carcinoma (in adolescents, though more common in adults). All of these tumors require surgical resection.
After completing the diagnostic tests, a surgical biopsy is planned. If the Wilms Tumor involves only one kidney and is not excessively large or extending far into major blood vessels, surgery will entail removal of the entire tumor along with the involved kidney. Children do very well with one remaining kidney. If the tumor is too large to resect or involves both kidneys, we will take a small biopsy and then use chemotherapy to shrink the tumor(s), followed by a second surgery 6-9 weeks later. A central line will be placed to allow chemotherapy.
Based on the results of the imaging studies and surgery, a clinical stage will be assigned:
- Stage I tumor completely removed
- Stage II tumor grew through the kidney capsule but was completely removed
- Stage III residual abdominal tumor (due to lymph node spread, spillage of
tumor cells into the abdomen, or a tumor too large to resect)
- Stage IV tumor spread to the lung or the liver
Evaluation of the tumor by the pathologist will allow assignment of a tumor grade, either favorable histology (FH, 96% of patients) or unfavorable histology (UH, 4% of patients).
Therapy and Prognosis
Therapy is based on tumor stage and grade. Patients are given the opportunity to enroll on Children’s Oncology Group therapy protocols or may choose to be treated off protocol with standard of care therapy as summarized below:
- Stage I Vincristine and Actinomycin D intravenously, over 22 weeks
- Stage II Vincristine and Actinomycin D intravenously, over 22 weeks
- Stage III Vincristine, Actinomycin D, and Adriamycin, intravenously over 28 weeks, and abdominal radiation
- Stage IV Vincristine, Actinomycin D, and Adriamycin, intravenously over 28 weeks, with abdominal and lung radiation (if there is lung metastasis)
- UH Vincristine, Actinomycin D, Adriamycin, Etoposide, Cyclophosphamide, intravenously over 33 weeks, and radiation therapy
The overall cure rate is approximately 85%, with about 90% of Stage I, 99% of Stage II, 85% of Stage III, 66% of Stage IV, and 66% of unfavorable histology (UH) patients cured.
Therapy for Relapse
Patients with initial Stage I or Stage II Wilms Tumor who relapse can still be cured using more intense chemotherapy. Patients with initial Stage III or IV or UH Wilms Tumor who relapse can still be cured, with use of intense chemotherapy followed by an autologous stem cell transplant (this involves harvesting the patient’s blood or marrow stem cells, followed by very high dose chemotherapy, and finally re-infusion of the patient’s own stem cells to rescue the blood counts).
Once therapy is complete, patients are followed for recurrence with chest CT scans and chest X-rays and with abdominal ultrasound, every 3 months for the first 3 years and then every 6 months for the next 2 years, after which the patient is still followed by history and physical examination. Blood tests and urinalyses are also obtained at each visit. If Adriamycin was given, then cardiac echo and EKG tests will be done every 2-3 years. The large majority of patients have few long-term side effects from their therapy.