**12. Renal failure**

Renal function is an important consideration in survivors of WT, particularly in those who develop progression of bilateral WT or receive RT to the opposite kidney in unilateral disease. Non-syndromic children with unilateral WT treated with radical nephrectomy without nephrotoxic chemotherapy or RT are at low risk for significant long-term renal dysfunction [50]. Although a significant number of survivors have subclinical glomerular and tubular damage [51, 52], the risk of end-stage renal disease (ESRD) is very low in most patients with unilateral WT. A study on 5910 patients enrolled in NWTS showed that the 20-year cumulative incidence of end-stage renal disease (ESRD) after unilateral WT was 74% in children with Denys Drash syndrome, 36% in children with WAGR syndrome, 7% in male patients with hypospadias or cryptorchidism and 0.6% in non-syndromic WT patients. Twenty-year cumulative incidence of ESRD after bilateral Wilms tumor was 50% in children with Denys Drash syndrome, 90% in children with WAGR syndrome, 25% in male patients with

hypospadias and cryptorchidism and 12% in other non-syndromic patients [53]. A subsequent NWTS study assessed risk factors for ESRD in those without known WT1-related syndromes; it was found that patients with characteristics associated with a WT1 etiology (stromal predominant histology, intralobar nephrogenic rests and WT diagnosis at <24 months) had a higher risk of ESRD due to chronic renal failure [54]. In other reports from the CCSS and Denmark, renal tumor survivors after 18–20 years after treatment with nephrectomy and abdominal RT, had good renal function based on estimated glomerular filtration rates, although eGFR was significantly lower than in the normal population. WT survivors also had higher rates of albuminuria and hypertension [55, 56].
