Adherence to Protocol Recommendations for Children With Wilms Tumour in Two Consecutive Studies in the United Kingdom and Ireland—Does Variation Matter?

BACKGROUND AND AIMS: Wilms tumour (WT) has excellent event-free and overall survival (OS). However, small differences exist between countries participating in the same international study. This led us to examine variation in adherence to protocol recommendations as a potential contributing factor. METHODS: Retrospective analysis of risk-stratified chemotherapy and radiotherapy regimens given to children with unilateral WT treated with pre-operative chemotherapy in the SIOPWT2001 (2002-2011) and Improving Population Outcomes for Renal Tumours of Childhood (IMPORT) (2012-2018) studies in the United Kingdom and Ireland. Pre- and post-operative treatments were classified as per protocol (PP), deviation (PDEV)-variation for specified clinical reasons, violation (PVIOL)-not treated PP. RESULTS: A total of 1256 children with WT were registered by 20 centres. A total of 1052 (84%) had unilateral WT treated with pre-operative chemotherapy. All had centrally reviewed pathology. Case report forms allowing categorisation of the whole treatment pathway were available for 756 (72%) patients. Treatment was classified as PP in 452 (60%), PDEV in 175 (23%) and PVIOL in 129 (17%). Stage III/IV tumours had higher proportion PVIOL (21% and 35%, respectively) compared to Stage I/II tumours (8%-10%). Two-thirds of patients were treated in 'high-volume' centres (≥5 new WTs/year). Protocol adherence rates were similar between high- and low-volume centres. Protocol adherence category had no impact on event-free or OS. CONCLUSIONS: Protocol guidelines are followed closely for lower stage tumours, but there is greater variation in advanced disease. Centre size showed no association with survival, emphasising the effectiveness of using a national treatment protocol, supported by central pathology review.