Wilms Tumor

The most frequent finding is a painless, palpable abdominal mass.

Less frequent findings (in approximately 20% of patients) include abdominal pain, hematuria, fever, anorexia, nausea, and vomiting (1). Hematuria can be microscopic or gross. Hypertension may occur and is of variable severity.

• History and physical examination

• Abdominal ultrasound, CT, or MRI

• Blood tests

• Tumor pathology and molecular profiling

Physical examination often leads to the diagnosis, and some findings (eg, aniridia, urogenital abnormalities, overgrowth or hemihypertrophy) may suggest associated or predisposing conditions.

Abdominal ultrasound with Doppler determines whether the mass is cystic or solid and whether the renal vein or vena cava is involved. Abdominal CT or MRI (MRI is preferred) is needed to determine the extent of the tumor and check for metastasis to regional lymph nodes, the contralateral kidney, or liver (1).

Chest CT is recommended to detect metastatic pulmonary involvement at initial diagnosis (1).

Fluorodeoxyglucose-positron emission tomography (FDG-PET) and bone scans are occasionally performed to evaluate for distant metastases.

Blood tests include complete blood count, liver and kidney tests, and sometimes urine catecholamines to exclude neuroblastoma (1, 2).

Diagnosis of Wilms tumor is typically made presumptively based on the results of the imaging studies.

Nephrectomy rather than biopsy is performed in most patients at the time of diagnosis. Biopsy is not routinely performed before nephrectomy because of the risk of peritoneal contamination by tumor cells, which would spread the cancer and thus change the stage from a lower to a higher one, requiring more intensive therapy. Exceptions to this include patients with unresectable unilateral disease, suspected bilateral disease, or an uncertain diagnosis. For patients with bilateral disease, biopsy is important to confirm the histology before starting chemotherapy.

During surgery, local and regional lymph nodes are sampled for pathologic and surgical staging (2). Molecular profile with genetics is typically analyzed once the tumor has been resected.

The Children's Oncology Group (COG) staging system is based on tumor extent, resectability, and spread (1) and ranges from stage I to stage V:

• Stage I: Completely resected unilateral tumor confined to the kidney

• Stage II: Completely resected unilateral tumor extends beyond the kidney

• Stage III: Residual tumor in the abdomen (positive nodes/margins, spill, or biopsy/incomplete resection

• Stage IV: Distant metastases

• Stage V: Bilateral disease

• Surgery and chemotherapy

• Sometimes radiation therapy

The initial treatment approach to unilateral Wilms tumor can vary by country or region. Most clinical trials for treatment of children with Wilms tumor have been conducted by the Children's Oncology Group (COG) in the United States and by the International Society for Paediatric Oncology (SIOP) in Europe. In the COG treatment protocol, resection of all unilateral tumors is performed first, whereas in the SIOP treatment protocol, preoperative chemotherapy is given first to patients > 6 months old. Both groups recommend postoperative chemotherapy except in select cases (1, 2).

Radiation therapy is used to improve local control in certain cases depending on risk stratification, as well as to treat metastatic sites of disease.

Although rare, a select group of young patients (< 2 years of age) with small tumors (< 550 g) and stage I favorable histology can be cured by surgery alone (3, 4).

The type of chemotherapy and the length of therapy depends on tumor histology and stage. The chemotherapy regimen depends on the risk group but usually consists of actinomycin D (dactinomycin) and vincristine with or without doxorubicin (1, 2). For more aggressive tumors, intensive multiagent chemotherapy regimens are used.

Children with very large, nonresectable tumors or bilateral tumors are candidates for chemotherapy followed by re-evaluation and delayed resection.

Children who have higher-stage disease or tumors involving the regional lymph nodes are given radiation therapy.

Prognosis for Wilms tumor depends on:

• Histology

• Stage at diagnosis

• Age (older age associated with a worse prognosis)

• Molecular findings

The outcome for children with Wilms tumor is excellent. The 4- to 5-year event-free survival rate for lower-stage disease (localized to the kidney) is > 95% (1). Even children with more advanced disease can fare well; reported 5-year survival rates range from < 75% (high-risk histology) to > 90% (low-risk histology) (2).

Of molecular markers, chromosome 1q gain has been validated as the most prevalent adverse prognostic biomarker in favorable-histology Wilms tumor (approximately 28% of tumors) and is associated with worse prognosis across all stages (3). Other molecular markers associated with poorer outcomes include loss of heterozygosity at chromosomes 1p, 11p15, and 16q (4).

Wilms tumor may recur, typically within 2 years of diagnosis. It is usually detected during routine follow-up surveillance imaging (5). Cure is possible in children with recurrent cancer. Outcome after recurrence is worse for children who relapse earlier, develop symptoms, or have more advanced or histologically unfavorable disease at relapse.

The following English-language resource may be useful. Please note that The Manual is not responsible for the content of this resource.

1. National Cancer Institute (NCI): Wilms Tumor and Other Childhood Kidney Tumors Treatment (PDQ)-Health Professional Version: Wilms Tumor