Survival for Children Diagnosed With Wilms Tumour (2012–2022) Registered in the UK and Ireland Improving Population Outcomes for Renal Tumours of Childhood (IMPORT) Study

ABSTRACT Background The Improving Population Outcomes for Renal Tumours of childhood (IMPORT) is a prospective clinical observational study capturing detailed demographic and outcome data on children and young people diagnosed with renal tumours in the United Kingdom and the Republic of Ireland. Methods Data were extracted from the IMPORT database for all newly diagnosed cases of Wilms tumour (WT) registered between November 2012 and December 2022. Kaplan–Meier survival was estimated at one, three and five years. For children aged 0–14 years with unilateral WT, Cox proportional hazards models were used to examine patient/tumour characteristics in relation to the excess hazard of death. Results Among 620 patients, 570 had unilateral and 50 (8%) bilateral disease; 582 (94%) patients received pre‐operative chemotherapy and 38 (6%) immediate surgery. Median age was 41 months (IQR: 41–65). Median tumour volume at diagnosis was 595 cm 3 (IQR: 348–914) and 228 cm 3 (IQR: 83–535) after pre‐operative chemotherapy, with 123/443 (28%) ≥500 cm 3 . Of 570 patients with unilateral WT, 419 (73.5%) had localised and 151 (26.5%) metastatic disease. Five‐year survival was highest for children aged 0–4 years (94.8%). Five‐year survival by Toronto stage (assessed at nephrectomy) was 97.0% (stage I/yI), 93.8% (stage II/yII), 85.2% (stage III/yIII) and 88.9% (stage IV), and by histology 74.6% (high risk), 95.2% (intermediate risk) and 100% (low risk). In univariate analysis, histological risk group, age (</≥ 4 years), stage and tumour volume ≥500 cm 3 after pre‐operative chemotherapy were significantly associated with excess risk of death. In multivariate modelling, only high‐risk histology (HR 10.8, 95% CI: 4.0–29.1) retained significance. Conclusions Five‐year survival for children with WT in the United Kingdom and Ireland is generally above 90%, with high‐risk histology as the most important adverse prognostic factor. However, median tumour volume at diagnosis and after pre‐operative chemotherapy remains large.