Treatment of Wilms Tumor
Table 3. Overview of Wilms Tumor Standard Treatment by Stage continued...
Treatment has changed from an initial surgical approach to an attempt to shrink the tumor and spare renal parenchyma with preoperative chemotherapy. The first COG trial to formally study bilateral Wilms tumors (COG-AREN0534) reflects the present recommendation to not perform an initial biopsy or laparotomy. Primary tumor excision should not be attempted, but patients should be given preoperative chemotherapy consisting of vincristine, dactinomycin, and doxorubicin. In a series of 49 patients with Wilms tumor who received preoperative therapy according to the SIOP-93-01 guidelines, the timing of surgery was determined when there was no longer imaging evidence of tumor regression. The mean treatment duration was 80 days prior to nephron-sparing surgery. The 5-year EFS rate was 83.4% and the OS rate was 89.5%. All but one of the patients had nephron-sparing surgery in at least one kidney. Despite the good survival, 14% of the patients developed end-stage renal disease. In another series, nine out of ten patients with bilateral favorable-histology Wilms tumors underwent successful bilateral nephron-sparing procedures after receiving preoperative chemotherapy as detailed in a retrospective review from St. Jude Children's Research Hospital. One patient in the series developed renal failure after bilateral nephron-sparing surgery. Two patients with anaplastic histology died, although one patient died from complications of treatment rather than tumor. The OS for this group of patients was 83%. The authors recommend that bilateral nephron-sparing surgery should be considered for all patients who have bilateral Wilms tumor with favorable histology, even if preoperative imaging studies suggest that the lesions are unresectable.
For patients who are treated with preoperative chemotherapy, it is essential to evaluate the tumor pathology after 4 to 8 weeks. The ideal time to do a biopsy or resection is not clear for patients who are not being treated on a protocol, since minimal shrinkage may reflect chemotherapy-induced differentiation or anaplastic histology. However, continuing therapy without evaluating tumor pathology in a patient with bilateral Wilms tumor may increase toxicity for the patient without providing additional benefit for tumor control. Anaplastic histology occurs in 10% of patients with bilateral Wilms tumor and responds poorly to chemotherapy. Once the diagnosis is made, a complete resection should be performed. Making the diagnosis is not straightforward, since in a series of 27 patients from NWTS-4, discordant pathology was seen in 20 cases, which highlights the need to obtain tissue from both kidneys. Seven children who were eventually found to have diffuse anaplastic tumors had core biopsies performed to establish the diagnosis but anaplasia was not found on the core biopsies. Anaplasia was identified in only three out of the nine patients when an open wedge biopsy was performed and in seven out of nine patients who had a partial or complete nephrectomy.