Wilms' tumor staging
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Shanshan Cen, M.D. [2]
Overview
There are 5 stages of wilms' tumor based on both the results of the imaging studies and the surgical and pathologic findings at nephrectomy.
Staging
- Staging of wilms tumor is done based upon:
- Extent of tumor anatomically.
- It is not done on the basis of its genetics, histology or molecular markers.
- Extensive disease and worse prognosis is denoted by a higher stage.
- Patients suffering from a higher stage tumor get more aggressive treatment modalities.
- The staging systems that are currently used are:[1]
- National Wilms Tumor Study (NWTS) system.
- International Society of Pediatric Oncology (SIOP) system.
- The staging system was originally developed by the NWTS Group and is still used by the COG.
- There are two major systems currently in use (table 2) [77]: ●National Wilms Tumor Study (NWTS) – The NWTS system is based upon surgical evaluation prior to the administration of chemotherapy. It is used throughout the United States and Canada. ●International Society of Pediatric Oncology (SIOP) – The SIOP system is based upon post-chemotherapy surgical evaluation and is used extensively in Europe. Direct comparisons of trials using the two systems are difficult due to the difference in the timing of chemotherapy relative to surgical evaluation [78,79].
Stage 1 (43% of patients)
- For stage 1 Wilms' tumor, 1 or more of the following criteria must be met:
- Treatment: Nephrectomy + 18 weeks of chemotherapy
- Outcome: 98% 4-year survival; 85% 4-year survival if anaplastic
Stage II (23% of patients)
For Stage II Wilms' tumor, 1 or more of the following criteria must be met:
- Tumor extends beyond the kidney but is completely excised.
- No residual tumor apparent at or beyond the margins of excision.
- Any of the following conditions may also exist:
- Tumor involvement of the blood vessels of the renal sinus and/or outside the renal parenchyma.
- The tumor has been biopsied prior to removal or there is local spillage of tumor during surgery, confined to the flank.
Treatment: Nephrectomy + abdominal radiation + 24 weeks of chemotherapy
Outcome: 96% 4-year survival; 70% 4-year survival if anaplastic
Stage III (23% of patients)
For Stage III Wilms' tumor, 1 or more of the following criteria must be met:
- Unresectable primary tumor.
- Lymph node metastasis.
- Positive surgical margins.
- Preoperative chemotherapy has been given.
- Tumor spillage involving peritoneal surfaces either before or during surgery, or transected tumor thrombus.
Treatment: Abdominal radiation + 24 weeks of chemotherapy + nephrectomy after tumor shrinkage
Outcome: 95% 4-year survival; 56% 4-year survival if anaplastic
Stage IV (10% of patients)
Stage IV Wilms' tumor is defined as the presence of hematogenous metastases (lung, liver, bone, or brain), or lymph node metastases outside the abdominopelvic region.
Treatment: Nephrectomy + abdominal radiation + 24 weeks of chemotherapy + radiation of metastatic site as appropriate
Outcome: 90% 4-year survival; 17% 4-year survival if anaplastic
Stage V (5% of patients)
Stage V Wilms’ tumor is defined as bilateral renal involvement at the time of initial diagnosis. Note: For patients with bilateral involvement, an attempt should be made to stage each side according to the above criteria (stage I to III) on the basis of extent of disease prior to biopsy. The 4-year survival was 94% for those patients whose most advanced lesion was stage I or stage II; 76% for those whose most advanced lesion was stage III.
Treatment: Individualized therapy based on tumor burden
Stage I-IV Anaplasia
Children with stage I anaplastic tumors have an excellent prognosis (80-90% five-year survival). They can be managed with the same regimen given to stage I favorable histology patients.
Children with stage II through stage IV diffuse anaplasia, however, represent a higher-risk group. These tumors are more resistant to the chemotherapy traditionally used in children with Wilms’ tumor (favorable histology), and require more aggressive regimens.