What is Wilms Tumor?
Wilms tumor, also known as nephroblastoma, is the most common type of kidney cancer in children. In fact, it’s not only the most common cancer found in children’s stomachs, but it’s also the fourth most common cancer in children overall. This type of cancer is usually discovered in children who are younger than five years old. The name “Wilms tumor” comes from Dr. Max Wilms, a German doctor who first identified this disease in 1899.
What Causes Wilms Tumor?
Wilms tumor is a type of kidney cancer that predominantly affects children. While the exact cause is not known, it is believed that changes in certain genes that control the development of the urinary (genitourinary) tract could be responsible. These genes include WT1, CTNNB1, WTX, TP53, and MYNC, with WT1, CTNNB1, and WTX being altered in roughly one-third of all cases of Wilms tumor. It’s important to note, however, that only about 1% of children with Wilms tumor have a family member who also had the disease – and typically, it’s not one of their parents.
It’s thought that Wilms tumor develops from abnormally persistent tissue, or “nephrogenic rests”, in the developing kidneys. These are present in about 1% of infant kidneys, but they usually disappear as the child grows. However, these abnormal cells are found in up to 100% of cases of Wilms tumor affecting both kidneys, but only 35% of tumors affecting just one kidney.
Certain physical characteristics and disorders are linked to Wilms tumor, including large body parts on one side of the body (hemihypertrophy), absence of the iris part of the eye (aniridia), undescended testes (cryptorchidism), an abnormal kidney shape (horseshoe kidney), and a misplaced opening of the penis (hypospadias). However, these associations don’t necessarily mean they cause the cancer.
Cases of Wilms tumor where both kidneys are affected are rare, comprising only about 5% of all cases. This type is more commonly found in girls.
Risk Factors and Frequency for Wilms Tumor
Wilms tumor, a type of stomach cancer, is the most common cancer of this kind in children and generally appears between the ages of 3 and 5. Every year in the U.S, around 650 new cases of Wilms tumor are reported. Surprisingly, girls are a bit more likely to get Wilms tumor than boys. Wilms tumor is more prevalent among African and African American children, while East Asian children are the least affected. However, the rate of this cancer is almost similar across Europe and North America.
The majority of Wilms tumors, about 90%, are diagnosed before the child reaches the age of six. Typically, the diagnosis happens around the age of 3.5 years. Thanks to advancements in chemotherapy, a huge percentage of children with Wilms tumor now survive. Statistically, the 5-year survival rate in the U.S is 92%. However, in less privileged parts of the world, where resources are scarce, this rate drops to 78%.
Wilms tumor has been associated with various medical syndromes such as WAGR, Denys-Drash, and Beckwith-Wiedemann syndromes. In children with these syndromes, the likelihood of developing Wilms tumor is significantly increased. Wilms tumor can also be associated with genital irregularities in boys, such as undescended testes, unusually large veins in the scrotum, and abnormal urethra opening. Girls with Wilms tumor can often have abnormal uterus structures from birth.
- WAGR syndrome is identified by a specific abnormality in the WT1 gene, which plays a role in both kidney and gonad development. Children with this syndrome have an equal (50%) chance of developing Wilms tumor.
- Denys-Drash syndrome includes symptoms like male pseudo-hermaphroditism and progressive kidney failure from infancy. In 9 out of 10 cases, individuals with this syndrome will develop Wilms tumor.
- Beckwith-Wiedemann syndrome is characterized by asymmetric body growth, enlarged pancreas, large kidneys, outpouching of the naval ring, creases in ears, and having a larger than usual body and tongue from birth. Patients with this syndrome have a 5% to 10% chance of developing Wilms tumor.
Besides, other syndromes such as Sotos, Perlman, Trisomy 18 (Edward’s syndrome), Frasier, Bloom, Li-Fraumeni, and Simpson-Golabi-Behmel syndromes are also sometimes linked with Wilms tumor.
Other kidney abnormalities, like kidney duplication and misplaced kidneys, are also not rare in children suffering from Wilms tumor. Moreover, children less than a year old, if detected with kidney cells clusters (perilobar nephrogenic rests), have a significantly higher risk of developing Wilms tumor in their other kidney.
Signs and Symptoms of Wilms Tumor
Wilms tumor is a type of kidney tumor typically found in children. Most commonly, this condition doesn’t result in any symptoms and is usually discovered as a lump in the child’s abdomen, often by the parent during a bath. However, in some instances, there might be symptoms including:
- Abdominal pain
- Blood in urine
- Urinary tract infections
- A type of male groin swelling called varicocele
- High or low blood pressure (In about 1/3 of patients, high blood pressure goes back to normal after the tumor is removed)
- Fever
- Anemia (a low red blood cell count)
- In cases where the tumor has spread to the lungs, shortness of breath or rapid breathing
Among these, the most common first symptoms are abdominal pain (found in 30-40% of patients), high blood pressure (found in 25% of patients), and blood in urine (found in 12-25% of patients).
Testing for Wilms Tumor
In order to assess if your child has a Wilms tumor (a type of kidney cancer in children), your doctor may need to order certain tests, even though these tests aren’t specifically designed to detect this tumor. They’re necessary to rule out other causes of the symptoms. The tests your doctor may order include:
- A complete blood count test – this is done to check for anemia, a condition where you lack enough healthy red blood cells to carry enough oxygen to your body’s tissues.
- A chemistry profile – this is a group of tests that measures different chemicals in the blood to assess how well your body’s organs are working and to check for diseases.
- Tests on the kidneys’ function
- Urinalysis – a test of your urine that could show potential problems or diseases in your kidneys or urinary system.
- Coagulation studies – these tests measure how fast your blood clots to make sure your blood isn’t clotting too slowly or quickly.
- Cytogenetics studies – a type of lab test that investigates the structure and number of chromosomes in cells to identify any genetic disorders – in this case, they look for deletions in the 1p and 16q regions of the chromosomes which may contribute to the tumor.
Other than these tests, imaging studies are crucial for diagnosis and to plan the best treatment option. Initial assessments often include renal ultrasonography, a type of ultrasound that looks at your kidney and bladder. This is followed by an X-ray of the chest to check if the tumor has spread (metastasized) to the lungs. This is necessary because the most common site where Wilms tumor spreads is the lungs.
In some cases, your doctor may also order an abdominal and chest CT scan, typically performed under sedation, or an abdominal MRI. CT and MRI are nearly equally effective in diagnosing Wilms tumor, and can provide necessary information before any surgical procedure is planned.
These imaging studies are essential in planning the surgery if it’s needed. Factors such as the size of the tumor, its spread to the other side (contralateral extension), and the displacement of major blood vessels can all potentially result in longer surgery, increased blood loss and more complications.
Bone metastases are not common in Wilms tumor but they are dangerous and usually occur later as a relapse or recurrence. Therefore, bone scans may also be recommended.
A promising imaging technique, called MRI diffusion studies, could potentially differentiate between Wilms tumor and neuroblastoma (another common type of abdominal cancer in children), as they have different treatments. These studies measure the apparent diffusion coefficient (ADC), a marker that indicates the movement of water within tissue. It has been suggested that a higher ADC value indicates the presence of Wilms tumor, while a lower value indicates neuroblastoma.
However, while these results are encouraging, further research is needed to confirm if this measurement can be considered as a reliable guide for diagnosis.
Treatment Options for Wilms Tumor
Wilms tumor, a type of kidney cancer, is commonly treated with a combination of surgery and chemotherapy. The first step of treatment is usually the surgical removal of the kidney (nephrectomy). Afterward, the patient typically undergoes systemic chemotherapy, which involves medication that kills cancer cells throughout the body. However, there are some treatment plans where chemotherapy is administered first, followed by surgery.
In some cases, doctors may also examine the other kidney to ensure that the cancer has not spread there. They might also take samples of the lymph nodes (small glands that produce and store cells that fight infections) near the aorta (the main blood vessel in the body), in order to determine the stage of the cancer and if it improves survival chances. But, if the tumor is detected early and imaging tests are negative, this sort of extensive exploration might not be needed.
Both traditional open surgery and less invasive surgical techniques seem to yield comparable results in terms of short-term health complications, death rate up to three years, hospital readmission rates, and the state of the surgical margins (the edge of the area from where the tumor has been removed). However, open surgery generally allows for more lymph nodes to be retrieved during the procedure.
Doctors generally don’t recommend routine biopsies (procedure in which small samples of tissue are removed for examination) unless in unusual circumstances. This is because once a biopsy has been performed, the cancer is automatically classified as Stage III, which requires both radiation and chemotherapy for treatment.
Patients may or may not receive radiation after surgery, depending on the type of tumor and how far it has spread. Starting radiation within 14 days of surgery might improve survival chances for patients who don’t have cancer in other parts of the body.
if the disease is more aggressive, combination chemotherapy (use of more than one drug) is usually administered. The initial round of chemotherapy typically includes drugs like vincristine and dactinomycin while Doxorubicin, cyclophosphamide, etoposide, and carboplatin are also used.
In children with Wilms tumor in both kidneys, immediate surgery isn’t performed. Some doctors might attempt high-dose chemotherapy hoping to kill the tumor cells and save the kidneys. Instant removal of both kidneys ordinarily would require the patient to undergo dialysis (a treatment to filter and clean the blood), so all possible efforts are made to preserve the kidneys. Researchers keep examining the kidneys to track whether the tumor is responding to the treatment or not. In certain cases, nephron-sparing surgery (which involves removing only the part of the kidney affected by cancer) can be performed.
Patients whose disease comes back after the initial combined therapy usually have a more challenging outlook compared to patients who are newly diagnosed with Wilms tumor.
Additionally, some people receiving treatment for Wilms tumor might experience hepatic veno-occlusive disease, a condition in which some of the small veins in the liver are blocked. Symptoms might include abdominal pain on the upper right side, yellowing of the skin and eyes (jaundice), buildup of fluid in the abdomen (ascites), weight gain, and/or an enlarged liver (hepatomegaly). Treatment for this condition generally involves managing and relieving the symptoms (supportive care).
What else can Wilms Tumor be?
Diagnosing Wilms tumor, a kind of kidney cancer common in children, can be challenging because it can appear similar to other types of kidney cancers. Here are some of them:
- Clear cell renal sarcoma: This is the second most common kidney cancer in children. However, it’s more dangerous than Wilms tumor because it has higher death and relapse rates. It often spreads to the bone.
- Rhabdoid renal tumors: These are very aggressive and usually seen in children under the age of two. At the time of discovery, they’re often spread to other parts of the body which leads to an 80% death rate within one year of diagnosis.
- Congenital mesoblastic nephroma: This is usually found in the first year of life, often detected by an ultrasound. It’s typically associated with high blood pressure and elevated renin levels, a hormone that helps control blood pressure.
- Renal cell carcinoma: While rare in children, it can be very advanced when detected. Children who have undergone radiation and chemotherapy treatment for neuroblastoma, another type of cancer, are at an increased risk.
- Renal medullary carcinoma: This is a very serious type of cancer that is typically found in people with sickle cell disease. It is often highly invasive and quickly spreads to other parts of the body.
It’s crucial for doctors to distinguish between these types of cancers to make the appropriate treatment plan.
What to expect with Wilms Tumor
The chances of survival when dealing with a tumor can depend on the type of tumor and its stage. Some types of tumors generally have a good rate of survival, between 86% and 99%. Other, more aggressive types, show survival rates that range between 38% and 84%, depending on how advanced the tumor is.
In around 1% of patients, tumors can lead to final-stage kidney failure, which is often due to the development of tumors in both kidneys, one after the other.
If a woman has a condition called Wilms tumor-aniridia syndrome, it can lead to changes in the ovaries and an increased risk of developing a certain type of tumor called gonadoblastoma.
A few factors can make the situation more difficult, including:
– A type of tumor called anaplastic, particularly in stages II to IV
– Diffuse anaplasia, which is a more widespread version of the disease, can be worse than a form that is more localized
– Certain genetic changes (Trust us, these are big medical words but they are genetic alterations in the cells)
– A higher stage of the tumor (certain types of tumors are usually found at stage I, while others typically present at stages III and IV)
– Being over two years of age
– A higher number of affected lymph nodes (part of your body’s immune system)
– A larger size of the tumor
– Even small areas of tumor may worsen the situation due to resistance to chemotherapy, a common cancer treatment.
Possible Complications When Diagnosed with Wilms Tumor
Radiation and chemotherapy can both improve the survival rates of patients with advanced Wilms tumor. However, they can also potentially increase the risk of other cancers developing later in life.
For instance, radiation therapy can increase the chance of getting bone, breast, colon, and thyroid cancers much later. It also heightens the risk of developing osteoporosis.
Chemotherapy, particularly using medications like dactinomycin, doxorubicin, and vincristine, also heightens the risk of getting other cancers. Additionally, these drugs can cause specific harmful effects, such as hearing issues with carboplatin, heart problems with adriamycin, and peripheral nerve damage with vincristine.
Additionally, around 5% to 10% of Wilms patients have a condition known as Von Willebrand’s disease, which can make treatment more complicated. The first treatment option is usually a drug called DDAVP. If this isn’t successful, a treatment known as cryoprecipitate (which contains a high concentration of Von Willebrand Factor) can be used.
Implications of Treatment:
- Increased risk of secondary cancers from radiation and chemotherapy
- Increased risk of osteoporosis from radiation therapy
- Hearing issues due to carboplatin
- Heart problems due to adriamycin
- Peripheral nerve damage due to vincristine
- Complication in treatment due to Von Willebrand’s disease
Recovery from Wilms Tumor
After surgery, the hospital staff will make sure to keep an eye on certain aspects of your health such as:
* Your blood pressure
* Your electrolyte levels, body temperature, and blood sugar
* How much urine you’re producing
If you’re diagnosed with a type of kidney cancer in children known as Wilms tumor, there will be a special schedule for follow-up doctor’s visits:
* You’ll visit every 3 months for 2 years after diagnosis
* Then, you’ll see the doctor every 6 months for the next 2 years
* Finally, you’ll visit the doctor once every 2 years
During these follow-up visits for Wilms tumor, the doctor may:
* Check your abdomen for any signs of the cancer returning or finding a tumor in the liver
* Listen to your lungs for signs of cancer spreading
* Feel your thyroid gland (in your neck) for any growths (if you had radiation therapy to the chest)
* For female patients who had radiation therapy to the chest, they will have a breast examination
* Check for a nerve condition called peripheral neuropathy (a side effect of a chemotherapy drug called Vincristine)
* Check for liver/veno-occlusive disease (a rare liver disorder) in patients with tumors on the right side who had radiation therapy
There will be various tests as part of your follow-up care. These may include:
* Abdominal ultrasound (recommended yearly)
* CT scan
* MRI
* Chest x-ray
* Liver function testing
* Kidney function blood tests
* Early fertility screening
* Hearing tests for patients who had a chemotherapy drug called carboplatin
* Heart function tests, such as an ultrasound of the heart or EKG, at least every 3 years for patients who had a chemotherapy drug called doxorubicin (Adriamycin)
* Early screening for colon cancer for patients who had radiation treatment to the abdomen (should start 10 years after radiotherapy treatment or by age 35, whichever is later)
If you had radiation therapy to the lung or chest, some additional tests may be done:
* Hormone tests (TSH and free T4) to check thyroid function
* Thyroid ultrasound every 3 years to screen for thyroid nodules or masses
* Bone density testing should be started 10 years earlier than usual because of the risk of early osteoporosis (a condition that weakens bones)
* Early screening for breast cancer in women.
