Characteristics and Survival of Patients With Wilms Tumor and Bone Metastases: A SIOP-RTSG 93-01, SIOP 2001, and UK-IMPORT Study.

Background Wilms tumor (WT) has an excellent outcome. Studies suggest that patients with WT and bone metastases (WT-BM) have a poor prognosis. This analysis describes the characteristics and outcome of patients with WT-BM, registered by the International Society of Paediatric Oncology-Renal Tumor Study Group (SIOP-RTSG) and UK-IMPORT STUDY.Methods We retrospectively assessed clinical characteristics and outcome of patients with WT-BM at diagnosis treated according to SIOP-RTSG 93-01, SIOP 2001/UK-IMPORT study protocols.Results Among 7399 patients diagnosed with WT between 1993 and 2019, 47 were identified with WT-BM (12 males/35 females), accounting for 3.3% of stage IV-WT. The median age at diagnosis was 63 months (24-292 months). Four patients (9%) had only BM involvement and 43 patients (91%) had multisite metastases. Local stage was I-II in 15 (32%) patients, stage III in 26 (55%) patients, and unknown in 6 (13%) patients. Preoperative chemotherapy consisted of three drugs in 95% of cases with available data (38/40). Histological subtyping identified low-risk (LR, n = 4), intermediate-risk (IR, n = 29), high-risk (HR, n = 7) tumors, unknown/others in seven patients. The majority had postoperative treatment according to protocol. Among 35 patients with data, 33 (94%) received any kind of radiotherapy. EFS and OS were 67% and 74% at 2 years, decreasing to 64% and 62% at five years. EFS at 2 years was 14% in the HR group and 84% in the IR group.Conclusions WT-BM is a rare condition. Awareness of its existence and multimodality treatment are warranted.