A great deal of progress has been made in treating Wilms tumor over the last 25 years. Nine out of ten children are successfully treated with surgery, chemotherapy and sometimes radiation therapy. Many improvements in treatments have resulted from the work of the National Wilms Tumor Study Group. Today, most children with Wilms tumor are enrolled and treated in a clinical trial, so that the best treatments available can be improved even further.
Wilms tumors are relatively rare, therefore it is important to seek care at an experienced children’s cancer center. A team approach that includes the child’s pediatrician as well as specialists at the children’s cancer center where the treatment will be provided is recommended. Once a Wilms tumor is discovered, children should begin treatment quickly. Wilms tumors are often quite large by the time they are discovered, and these tumors tend to grow rapidly.
The first goal is to remove the tumor from the involved kidney or major site, even if the cancer has spread (metastasized) to other parts of the body. Sometimes, the tumor can be too large to remove immediately and may have spread into nearby blood vessels, other vital structures, or may be found in both kidneys. For these patients, doctors sometimes use chemotherapy to shrink the tumor before removing it later in the course of therapy.
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Surgery is the main treatment for Wilms tumor. The most common operation for Wilms tumor is called a radical nephrectomy. In this procedure, a surgeon removes the cancer along with the entire kidney, the ureter (the tube that carries urine from the kidney to the bladder), and fatty tissue that surrounds the kidney.
At the time of the radical nephrectomy, a regional lymph node sampling is performed. In this procedure, the surgeon removes the lymph nodes next to the kidney. Lymph nodes are bean-sized glands that are part of the immune system and help to fight infections. Many cancers spread to the lymph nodes. Sampling the lymph nodes helps assess the degree of spread within the abdomen.
During surgery, the liver and the other kidney will also be examined. Any suspicious areas may be biopsied, meaning that tissue samples are removed for examination under a microscope.
If imaging tests such as a chest x-ray or CT scan suggest that the Wilms tumor has spread to the lungs, the surgeon may also take a tissue sample or remove the nodule completely. This may be done through a separate incision in the chest wall.
Knowing whether or not a Wilms tumor has spread to the lymph nodes, liver or the other kidney is important in determining the stage of the disease, as well as in choosing treatment.
Chemotherapy is drug therapy usually administered by injection. This means that the drugs used to treat the cancer are injected into the bloodstream where they circulate through the body to reach and destroy the cancerous cells.
Chemotherapy is given to all children with Wilms tumor. It may be given:
- To shrink a tumor too large to remove surgically
- After surgery to destroy any tumor cells that might be circulating in the body (called adjuvant therapy)
- To treat cancer that has spread to organs beyond the kidney
Chemotherapy medications are injected into a vein in different combinations and dosages at different times, depending on the type and stage of Wilms tumor. Chemotherapy is ordered by the pediatric oncologist and is usually given by a nurse. Most chemotherapy for Wilms tumor can be given in an outpatient setting; however, in some cases the patient must be hospitalized.
While chemotherapy kills cancer cells, it can also damage some normal cells. Careful attention is given to avoid or minimize side effects. The side effects of chemotherapy depend on the type of drugs, the amount taken and the length of time they are taken. It is important to tell the cancer care team if the child has any side effects. The side effects can often be treated or, prevented with other medicines.
- Stage I and II tumor treatment: The chemotherapy agents used for Wilms tumor treatment vary according to stage. Lower stage disease (stages I and II) with favorable histology is usually treated with two chemotherapy medicines, vincristine and dactinomycin. These medicines are given intravenously (into a vein), initially on a weekly schedule and then every 2-3 weeks. Most, if not all of the chemotherapy for stage I-II tumors, is done as an outpatient and the side effects are mild, usually not requiring hospitalization. Radiation therapy is not required in Stages I-II favorable histology disease.
- Stage III and IV tumor and unfavorable histology tumor treatment: Stage III and IV disease and unfavorable histology tumors, as well as clear cell sarcoma of the kidney and malignant rhabdoid tumor, are treated with 3 or more chemotherapy agents depending on stage and histology. Radiation therapy is given to the abdomen and to other sites of metastases (spread of the cancer). Chemotherapy is given by vein and can usually be given as an outpatient. Occasionally, treatment for these stages of disease requires hospitalization and is often associated with more serious side effects.
Medicines used for higher stage tumors include: vincristine, dactinomycin, doxorubicin, cyclophosphamide, carboplatin, etoposide or ifosfamide. The choice of medicines used depends on the stage and status of current research treatment protocols.
Radiation therapy uses x-ray light to kill cancer cells. External beam radiation therapy focuses energy onto the cancer using a radiation source outside the body. This type of radiation therapy is often used along with surgery in more advanced cases of Wilms tumor (stages III, IV and V) that have spread beyond the kidney or are not able to be completely removed at surgery. It is used in Stage I and II disease only if there is evidence of unfavorable histology.
Causes of Kidney Cancer
Researchers currently DO NOT know what causes Wilms tumor or other kidney tumors. Only a few risk factors for kidney tumors are known for sure. Children with some genetic syndromes and abnormalities present at birth are more likely to develop Wilms tumor than other children. The conditions are aniridia (absence of the iris, the colored part of the eye), abnormalities of the urinary tract, hemihypertrophy (enlargement of one side of the body), Beckwith-Wiedemann syndrome, Perlman syndrome, Denys-Drash syndrome and Simpson-Golabi-Behmel syndrome. Children with these conditions are more at risk for development of Wilms tumor, but these account for only a small fraction of cases. These syndromes usually require medical care, so parents would know if their child had one of them. Sometimes, a child is found to have an abnormality of the urinary tract that was present at birth but not noticed until the diagnosis of Wilms tumor was made.