Complete necrosis induced by preoperative chemotherapy in Wilms tumor as an indicator of low risk: Report of the International Society of Paediatric Oncology (SIOP) Nephroblastoma Trial and Study 9

Background. The SIOP Nephroblastoma therapeutic protocols include a period of preoperative chemotherapy followed by nephrectomy and a period of postop erative chemotherapy. From the outset, identification of low-risk groups ha s been an aim of the SIOP Nephroblastoma Trials and Studies. Now that 90% o f children with Wilms tumor can be cured, attention is even more focused on the identification of patients who could benefit from less aggressive post operative therapy, thus minimizing the morbidity and late effects associate d with treatment. The prognostic implications of total necrosis in nephrobl astoma after chemotherapy have not been investigated hitherto. Procedure. B etween November 1, 1987 and lune 30, 1993, 599 patients referred to the SIO P-9 Nephroblastoma Trial and Study were preoperatively treated and classifi ed as stages I-IV nonanaplastic Wilms tumor. Results. Of these 599 patients , pathologic examination of the nephrectomy specimen revealed a completely necrotic Wilms tumor (CNWT) with no viable tumor remaining in 59 (10%): the se comprised 37 stages I-III and 22 stage IV. Of these patients, 58 (98%) h ad no evidence of disease at 5 years vs. 90% for the rest of the cohort (P < 0.05). Stages I-III patients represented 63% of CNWT and had a 97% overal l survival rate. The only death was related to veno-occlusive disease and o ccurred in a stage patient in the month following nephrectomy. Stage IV pat ients represented 37% of CNWT (vs. only 10% of ail other cases of unilatera l nonanaplastic Wilms tumor) and had a 100% rate of survival. Children with CNWT were older (mean 59 months vs. 43 months); their tumor at diagnosis w as larger and had regressed more significantly at subsequent ultrasound exa mination. The data also uphold the hypothesis that Wilms rumors of blastemi c pattern are most aggressive, but also are extremely responsive to chemoth erapy. Conclusions. Patients with unilateral nonanaplastic WT that showed t otal necrosis following preoperative chemotherapy had excellent outcome and should benefit from less aggressive postoperative treatment in further tri als. Other very responsive tumors, such as Wilms with <10% viable tumor, sh ould also be assessed. Med. Pediatr. Oncol. 34:183-190, 2000. (C) Wiley-Lis s, Inc.