Clinical characteristics and outcomes of relapse in unilateral Wilms tumor: a single-institution report from 2010 to 2022

Background: Wilms tumor (WT) is the most common pediatric malignant renal tumor in children. Overall, the prognosis for recurrent WT remains poor, with an overall survival (OS) rate of approximately 50%. This study aimed to characterize the clinical features and outcomes of patients with relapsed unilateral WT. Methods: We conducted a retrospective study of patients diagnosed with and treated for relapsed unilateral WT at Beijing Children's Hospital between January 2010 and December 2022. Results: A total of 46 patients with recurrent WT were included in the study. The 5-year event-free survival (EFS) and OS rates from the time of first relapse were 44.5% [95% confidence interval (CI): 28.4-59.4%] and 54.7% (95% CI: 37.4-69.0%), respectively. Multivariable Cox proportional hazards regression analysis revealed that early relapse and nonoperative management after relapse were independent risk factors for a second recurrence. Patients who relapsed within six months had a significantly higher risk of second recurrence than those who relapsed after six months [hazard ratio (HR) 3.0; 95% CI: 1.1-8.8; P=0.03]. Patients who did not undergo surgery after relapse had a significantly higher risk of second recurrence than those who did (HR 3.9; 95% CI: 1.4-11.4; P=0.01). In addition, the only factor significantly associated with OS in this cohort was the histology of the initial tumor. Focal or diffuse anaplasia in the initial tumor was associated with a markedly higher risk of death (HR 10.3; 95% CI: 2.1-50.9; P=0.007). Conclusions: We emphasize the importance of identifying adverse risk factors for recurrent WT. Early relapse (within six months) and nonoperative management after relapse are independent predictors of a second recurrence. Furthermore, unfavorable histology of the initial tumor independently predicts mortality in recurrent WT.