SIOP approach

Based on the experience of previous SIOP trials, children who need radiation therapy undergo postoperative treatment to the flank and/or metastatic sites. The SIOP 1 to 9 trials demonstrated that preoperative radiation therapy or preoperative chemotherapy decreased the proportion of patients who developed tumor spillage, from more than 20% to 5%. The noninferiority of preoperative chemotherapy to preoperative radiation therapy in the SIOP 5 trial, and the concern over secondary malignancies with preoperative radiation therapy, led SIOP to recommend preoperative chemotherapy as the standard initial treatment.[222] Over time, the percentage of children who were treated with postoperative radiation therapy decreased, from more than 90% to 15% and 25% in SIOP trials 6 to 9, SIOP 93-01, and SIOP-2001, respectively.[220]

Abdominal radiation therapy has been omitted for patients with metastatic, local stage III Wilms tumor who had complete necrosis after 6 weeks of preoperative chemotherapy. It was also omitted in patients with stage III Wilms tumor who received 4 weeks of preoperative chemotherapy (n = 19) and had complete necrosis. The outcomes were excellent for both groups of patients with stage III Wilms tumor who had complete necrosis. The 5-year EFS and OS rates were 100% for patients with stage III disease and 95% for patients with metastatic local stage III disease.[272,273]