Wilms tumor, medically known as nephroblastoma, is a rare form of kidney cancer that primarily affects young children. It is the most common kidney cancer in the pediatric age group and the fourth most common childhood cancer overall. This type of tumor typically occurs in children between the ages of 3 and 4, with most cases diagnosed before age 6. While it can rarely affect older children or adults, its occurrence significantly decreases after age 5.
Associated Risk Factors and Symptoms
The exact cause of Wilms tumor is unknown, with most cases appearing sporadically due to genetic changes in kidney cells. However, a small percentage of cases are associated with specific genetic syndromes. For instance, children with WAGR syndrome (aniridia, genitourinary anomalies, and intellectual disabilities) have a 50% chance of developing Wilms tumor. Beckwith-Wiedemann syndrome and Denys-Drash syndrome are also linked to an increased risk.
The most common sign of Wilms tumor is a noticeable lump or swelling in the abdomen, which is painless. This abdominal mass may be discovered during a routine physical examination. Other symptoms include unexplained fever, blood in the urine, loss of appetite, elevated blood pressure, abdominal pain, nausea, vomiting, or fatigue.
The Diagnostic Process
The diagnostic journey for Wilms tumor begins with a thorough medical history review and a physical examination. During the physical exam, the doctor will check the child’s abdomen for any swelling or masses and measure blood pressure. These initial steps help determine if further investigation is warranted.
Following the physical examination, non-invasive imaging tests are used to visualize the kidneys and surrounding areas. An ultrasound is the first imaging test, as it uses sound waves and is radiation-free, effectively identifying an abdominal mass. If a mass is detected, a computed tomography (CT) scan or magnetic resonance imaging (MRI) scan may follow to provide more detailed views of the tumor, assess its size, and check for any spread to nearby lymph nodes or distant organs like the lungs.
Blood and urine tests are also used to evaluate the child’s overall health and kidney function. Urine samples are analyzed for blood cells or proteins. Blood tests assess general health, including for conditions like anemia. While imaging tests can strongly suggest a Wilms tumor, a definitive diagnosis is confirmed by examining the tumor tissue under a microscope after it has been surgically removed.
Treatment Approaches
Treatment for Wilms tumor is effective and is tailored based on the tumor’s stage. Stage I indicates the tumor is completely removed and confined to one kidney, while Stage IV means the cancer has spread to distant organs such as the lungs, liver, or bones. Stage V involves tumors in both kidneys at diagnosis.
Surgery is a primary treatment component, involving nephrectomy, the surgical removal of the affected kidney and sometimes surrounding tissues. In cases where the tumor is large or present in both kidneys, chemotherapy may be administered before surgery to shrink the tumor, making its removal easier and potentially preserving kidney function. For infants under 6 months, surgery might be the initial step.
Chemotherapy, involving drugs like vincristine and dactinomycin, is used to destroy cancer cells throughout the body and reduce the risk of recurrence. It is given both before and after surgery, with the duration and specific drugs varying depending on the tumor’s stage and microscopic characteristics. Radiation therapy, using high-energy beams to kill cancer cells, is reserved for more advanced stages of Wilms tumor or when the tumor shows aggressive features. It may be given after surgery, particularly if the tumor has spread or has certain microscopic appearances.
Understanding Prognosis
The overall prognosis for children with Wilms tumor is excellent, with high survival rates due to advancements in treatment. For localized cases, survival rates can exceed 90%. However, the specific outlook for each child depends on several factors, including the cancer’s stage at diagnosis and the tumor’s histology.
Histology refers to how the cancer cells appear under a microscope, categorized as “favorable” or “anaplastic” (unfavorable). Tumors with favorable histology, which account for about 90% of cases, have a better prognosis, with survival rates ranging from 86% to 99% depending on the stage. Anaplastic histology, characterized by abnormal, rapidly dividing cells, is associated with a higher risk of relapse and a less favorable outcome, with survival rates ranging from 38% to 84% based on stage. Diffuse anaplasia, where anaplastic cells are widespread, carries a worse prognosis than focal anaplasia.
Long-term follow-up appointments are regular care after treatment to monitor the child’s health and detect late effects of therapy. These follow-ups help manage long-term health concerns from treatments like chemotherapy and radiation, such as an increased risk of secondary cancers or cardiac issues in adulthood. Regular monitoring ensures continued well-being for survivors.