De-Escalated Radiotherapy for Advanced Stage Wilms Tumor: A Single-Center Experience.

PURPOSE/OBJECTIVE(S) Survival rates have dramatically improved in Wilms tumor (WT) with multimodal treatment. Herein, we aimed to compare the efficacy of 9 Gy to 10.8 Gy flank RT or whole abdominal irradiation (WAI) in patients with WT treated in a single tertiary treatment center. MATERIALS/METHODS This study includes 42 patients with a unilateral or bilateral WT with a local stage III disease who received a low-dose (10.8 Gy) or lower-dose (9 Gy) flank RT or WAI between 1998 and 2018. Patients had undergone either upfront surgery followed by adjuvant chemotherapy (CXT) or neoadjuvant CXT followed by surgery. Patients with lung metastasis without a complete response to CXT also received whole lung irradiation (WLI) of 9-12 Gy. RESULTS The disease was staged as III in 22, IV in 12, and V in 9 patients, respectively. After a median follow-up of 75 months, the 2- and 5-year overall survival, locoregional relapse-free survival, and distant metastasis-free survival rate was 92% and 79%, 87% and 76%, and 75% and 69%, respectively. None of these survival rates were different among 9 Gy and 10.8 Gy doses. Among patients receiving WLI, the lung relapse rate was also similar between < 12 Gy and 12 Gy of irradiation. Late toxicity was observed in four (10%) patients as scoliosis, cardiac dysfunction, renal injury and hypertension, and short stature. CONCLUSION De-escalated RT of 9 Gy to the flank or abdomen does not compromise oncologic outcomes in patients with a local stage III WT.