Factors possibly affecting prognosis in children with Wilms tumor diagnosed before 24 months of age: A report from the (AIEOP) Wilms Tumor Working Group

Background: Children with Wilms’ tumor (WT) aged under 24 months (infants) have a better prognosis than older patients. Our aim was to study the epidemiology of this age group, with focus on the modality of diagnosis, tumor size, and association with malformations/syndromes, seeking to understand if any of these factors might be related to prognosis. Patients and methods: Infants diagnosed with WT between 2003 and February 2010 were evaluated. A query form was used to collect data on the modality of WT diagnosis (symptomatic or incidental), tumor volume, maximum diameter, site, and stage. Results: Data were collected for 117 of 124 WT infants registered. Twenty-four cases had an incidental diagnosis (ID) of renal mass, usually arising from an abdominal ultrasound performed for other reasons, and 93 had been diagnosed based on clinical signs/symptoms. The incidental cohort displayed unifocal disease, mean tumor diameter 5.52 cm, mean tumor volume 84.30 ml, and 14 patients showed associated malformations. Symptomatic patients had mean maximum tumor diameter of 10.18 cm, mean tumor volume of 451.18 ml, and six had associated malformations. Conclusions: Our study showed that 20% of the infants had an ID of WT; they had a relatively smaller nonmetastatic tumor and a higher rate of malformations than infants of the symptomatically diagnosed group, but we did not detect any difference in age at diagnosis between the two groups. Conversely, we found a significant difference in the 5-year event-free survival rate (P = 0.018) between infants under 1 year (96%), more frequently associated with congenital malformations, and infants 1–2 years (80%).