Because of the relative rarity of this tumor, all patients with Wilms tumor should be considered for entry into a clinical trial. Treatment planning by a multidisciplinary team of cancer specialists (pediatric surgeon or pediatric urologist, pediatric radiation oncologist, and pediatric oncologist) with experience treating Wilms tumor is required to determine and implement optimum treatment.
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The majority of the randomized clinical studies for treatment of children with Wilms tumor have been conducted by two large clinical groups. The National Wilms Tumor Study (NWTS) Group, which is now part of the Children's Oncology Group (COG), has established standard treatment for Wilms tumor in North America, which consists of initial surgery followed by chemotherapy and, in some patients, radiation therapy.[1,2,3] The Soci�t� Internationale d'Oncologie P�diatrique (SIOP) is a European consortium. There are differences between the two groups that affect staging and classification. The SIOP trials provide preoperative chemotherapy before definitive resection. This statement will focus on the NWTS (now COG Renal Tumor Committee) results and studies. The major treatment conclusions of the National Wilms Tumor Studies (NWTS 1-5) are as follows:
Routine, postoperative radiation therapy of the flank is not necessary for children with stage I tumors or stage II tumors with favorable histology (FH) when postnephrectomy combination chemotherapy consisting of vincristine and dactinomycin is administered.
The prognosis for patients with stage III FH is best when treatment includes: (a) dactinomycin, vincristine, doxorubicin, and 10.8 Gy of radiation therapy to the flank; or (b) dactinomycin, vincristine, and 20 Gy of radiation therapy to the flank.
The addition of cyclophosphamide to the combination of vincristine, dactinomycin, and doxorubicin does not improve prognosis for patients with stage IV FH tumors.
A single-dose of dactinomycin per course (stages I-II FH, stage I anaplastic, stage III FH, stages III-IV, or stages I-IV clear cell sarcoma of the kidney) is equivalent to the divided-dose courses, results in the same event-free survival, achieves greater dose intensity, and is associated with less toxicity and expense.
Eighteen weeks of therapy is adequate for patients with stage I FH whereas other patients can be treated with 6 months of therapy instead of 15 months.[1,4,5,6,7]
Tumor-specific loss of heterozygosity for combined 1p and 16q predicts recurrence of FH Wilms tumor.
About 2% of Wilms tumors have ureteral involvement. Presence of gross hematuria, nonfunctioning kidney, or hydronephrosis suggests the tumor may extend into the ureter and cystoscopy is recommended. En bloc resection to avoid tumor spill is recommended.
Operative principles have evolved from NWTS trials. The most important role for the surgeon is to ensure complete tumor removal without rupture and perform an assessment of the extent of disease. Radical nephrectomy and lymph node sampling via a transabdominal or thoracoabdominal incision is the procedure of choice. A flank incision should not be performed because of the limited exposure it provides. For patients with resectable tumors, preoperative or intraoperative biopsy should not be performed. Routine exploration of the contralateral kidney is not necessary if technically adequate imaging studies do not suggest a bilateral process. If the initial imaging studies are suggestive of bilateral kidney involvement and depending on the size of the tumor, biopsy or wedge resection may be performed. Alternatively, the contralateral kidney should be explored to rule out bilateral involvement. This should be done prior to nephrectomy since the diagnosis of bilateral disease would dramatically alter the approach.