Research helps to increase survival rates
If a child has cancer of the kidney it is most likely something called Wilms tumor. Wilms tumor accounts for 95 percent of kidney and renal cancers in children under the age of 14. Also called “nephroblastoma,” Wilms tumor is a mass of cancer cells that grow in kidney tissue.
The kidneys filter and clean the blood and produce urine. Though there are a pair of kidneys — they are fixed to the back wall of the abdominal cavity, with one on each side of the backbone — in most cases of Wilms tumor only one kidney is affected.
This is a disease primarily of young children. At the time of diagnosis, most Wilms tumor patients are less than five years old.
Clinical trials over the past 22 years have been associated with improved long-term survival rates for children with Wilms tumor.
- Between 400-500 new cases of Wilms tumor are diagnosed each year in the U.S.
- About six percent of all cancers in children are Wilms tumor.
- Clinical trials over the past 22 years have been associated with improved long-term survival rates for children with Wilms tumor.
- The long-term survival has approached 90 percent for most patients, and 95 percent for those with the most favorable prognosis. Careful use of surgery and a combination chemotherapy and radiation therapy, where necessary, have produced these results.
The disease usually has no symptoms that are obvious to the child or parent. Instead, the hard mass of the tumor is most often felt by the physician’s hands during a routine exam of the abdomen. Parents might also find a lump in the belly. Only rarely will the child complain of fever, aches, or blood in the urine.
Unlike most cancers, Wilms tumor does not generally interfere with a child’s health — even though it may become very large. The average weight of a newly found tumor is one half pound — that’s four times larger than a kidney of the average three-year-old. Though large, the Wilms tumor cells do not tend to spread quickly. Most are found during the child’s annual physical exam when the doctor presses deeply into the child’s stomach area, above the navel.
Several tests are used to diagnose Wilms tumor. They are:
- Ultrasound: Sound waves directed at the tumor help make a picture of the tumor.
- CT Scan (computed tomographic scan): Similar to an x-ray, this machine produces pictures of soft tissues that will show irregular swellings and lumps — possible tumors — in the kidney.
- CT Scan of chest: This is used to look for possible spread of the tumor.
- MRI (magnetic resonance imaging): This uses magnetic waves to make a picture of the kidney.
- Chest and bone x-rays: These may be taken to determine if the Wilms tumor cells have spread to sites beyond the kidney.
- Surgery: If any of the procedures above show abnormal tissue, the doctor will usually try to surgically remove it. In some cancers, biopsies are done first, but with most cases of Wilms tumor, the surgeon attempts to take out all of the tumor instead of removing just a portion to examine under a microscope.
Once Wilms tumor is found, tests are done to determine the extent to which the cancer cells have spread from their point of origin to surrounding tissues, or to other parts of the body. This is called “staging” the cancer. Staging is an important step because it helps the child’s doctor recommend the most effective treatment approach. The stages of Wilms Tumor are:
- Stage I: Cancer has not spread. As a result, it can be completely surgically removed.
- Stage II: Cancer has spread to areas near the kidney — such as fat, blood vessels or a portion of the kidney that conducts fluid in and out of it known as the renal sinus. Despite the spread, Stage II cancers also can be completely removed by surgery.
- Stage III: Cancer has spread to areas near the kidney, including lymph nodes, but cannot be totally surgically removed because of the location of the cancer, or the extent of its spread. For example, if the cancer has invaded important blood vessels or spread throughout the abdomen, surgery may be too risky to the patient.
- Stage IV: Cancer has spread beyond the kidneys to other organs such as lung, liver, bone or brain.
- Stage V: Cancer cells are found in both kidneys (bilateral).
To learn more about Wilms tumor, read “Rosie’s story: surviving Wilms tumor.”
Histology or cell type
The histology or cell type refers to the biological characteristics of the cancer cells determined by evaluating certain characteristics of the cancer cells under a microscope. In the case of Wilms tumor, the way the cells look under the microscope says a lot about how the cancer will respond to treatment. Doctors break down Wilms tumor types into one of two categories:
- Favorable histology
- Unfavorable histology
This is a shorthand way of talking about what kind of cells are involved, and the likelihood for a cure. Unfavorable histologies are more challenging medical situations than favorable histologies. This unfavorable histology condition is known as anaplasia. About 95 percent of Wilms tumors lack anaplasia and therefore have favorable histologies. Other unfavorable conditions are clear cell sarcoma and rhabdoid tumor.
Treatment for Wilms tumor depends on the stage of the disease, the cell type (histology), and the age and overall health of the child. Whatever the stage, all patients with Wilms tumor have treatment options available to them. They consist of the following approaches, used singly, serially or in combination, depending on the location, stage and biological characteristics of the cancer cells.
- Partial nephrectomy: The cancer and part of the kidney nearest the cancer are removed. This operation is usually performed only in special cases, such as when the other kidney is damaged or has already been removed.
- Nephrectomy: A whole kidney is removed. The remaining kidney on the other side of the body performs the work of filtering the blood. In children, the remaining kidney will grow an additional ten or 20 percent to accommodate this extra work. A nephrectomy is the most common surgery for Wilms tumor.
- Chemotherapy:This method relies on powerful anti-cancer drugs that are usually injected into a vein. It is a “systemic” treatment — meaning it treats the whole body, or system, because the circulating blood carries the drugs throughout the entire body. Chemotherapy given after the cancer has been surgically removed is called adjuvant chemotherapy.
- High-dose chemotherapy: In some instances, very high doses of chemotherapy drugs will be used to kill cancer cells. A possible side-effect of this dose is destruction of the bone marrow, which is the blood-forming tissue inside the bones. To mitigate this effect, doctors can withdraw portions of the patient’s own bone marrow before therapy begins and freeze it. After the high-dose chemotherapy is over, the patient’s bone marrow will be reintroduced into the body by a needle in a vein. This is called an autologous bone marrow reinfusion.
- Radiation therapy: This is used to kill cancer cells and shrink the size of the tumor. Radiation relies on the use of x-rays and other high-energy rays generated by a machine outside of the body.
Treatment by stage
Stage I Wilms tumor
If the child has a favorable-histology tumor, or has anaplastic Wilms tumor, treatment will probably be surgery to remove the cancer followed by chemotherapy. If the child has either clear cell sarcoma of the kidney or rhabdoid tumor, treatment will probably be surgery to remove the cancer followed by radiation therapy plus chemotherapy.
Stage II Wilms tumor
If the child has a favorable-histology tumor, treatment will probably be surgery to remove the cancer followed by chemotherapy. If the child has an unfavorable histology tumor (anaplasia, clear cell sarcoma, or rhabdoid tumor of the kidney), treatment will probably be surgery to remove the cancer followed by radiation therapy plus chemotherapy.
Stage III Wilms tumor
If the child has a favorable- or an unfavorable-histology tumor (anaplasia, clear cell sarcoma, or rhabdoid tumor), treatment will probably be surgery to remove the cancer followed by radiation therapy plus chemotherapy.
Sometimes the cancer cannot be removed during surgery because it is too close to important organs or blood vessels or because it is too large to remove. In this case, the doctor may only perform a biopsy and then give chemotherapy with or without radiation therapy. Once the cancer has become smaller, surgery can be performed, followed by additional chemotherapy and radiation therapy.
Stage IV Wilms tumor
If the child has a favorable- or an unfavorable-histology tumor (anaplasia, clear cell sarcoma, or rhabdoid tumor), treatment will probably be surgery to remove the cancer followed by radiation therapy with chemotherapy. Patients whose cancer has metastasized to the lungs will receive additional radiation therapy.
Stage V Wilms tumor
Because both kidneys contain cancer, it is not usually possible to remove both kidneys. A piece of the cancer in both kidneys will probably be removed, along with some of the lymph nodes around the kidney to see whether they contain cancer. Following surgery, chemotherapy is given to shrink the cancer. A second operation is then performed to remove as much of the cancer as possible, while leaving as much of the kidneys as possible. Surgery may be followed by more chemotherapy and/or radiation therapy.
Recurrent Wilms tumor
If the child’s cancer comes back (recurs), treatment depends on the treatment the child received before, how much time has passed since the first cancer was treated, the histology of the cancer, and where the cancer came back. Depending on these factors, treatment may be surgery to remove the cancer, plus radiation therapy and chemotherapy.
This information is displayed with permission of the University of Minnesota Cancer Center. For more information about this disease or to review active clinical trials, please visit the website of the Cancer Center.