Non-Wilms Tumors of the Kidney in the Pediatric Population: A Review of Outcomes and Predictors of Survival

Objective: To determine the outcomes and predictors of survival for pediatric non-Wilms renal tumors. Methods: The Surveillance, Epidemiology, and End Results database (1973-2005) was queried for all patients under 20 years of age. Results: A total of 349 cases of pediatric non-Wilms renal tumors were identified. The major histologic groups include renal cell carcinomas (RCC) (44.1%), clear cell sarcoma (CCS) (17.2%), and malignant rhabdoid tumors (MRT) (11.5%). Overall, a bimodal age distribution was observed, with tumors commonly presenting in patients 2 year old or younger and in patients 16 years old or greater. However, greater than 50% of patients with RCC were diagnosed after the age of 15 years, whereas in patients with CCS or MRT, greater than 50% of these patients were younger than the age of 5 years. Of patients with CCS, a 3:1 predominance of male patients was observed. At the time of diagnosis, RCC (56.8%) and CCS (52.5%) tumors were more likely locally staged while MRT were more likely in advanced stages (51.3%, p<0.001). Overall 10-year survival for the entire cohort was 63% with improved survival observed in patients with CCS (79%) and RCC (70%) versus MRT (29%, p<0.001). By univariate analysis, surgical resection improves overall survival (10-year survival: 68% vs. 30%, p<0.001), while no difference was observed for patients undergoing radiotherapy (10-year overall survival: 60% vs. 63%, p=0.814). By multivariate analysis, worse overall survival was observed for patients >10 years old (HR 4.01, p=0.013) and those diagnosed with advanced disease (HR=12.78, p<0.001). In addition, patients diagnosed with MRT (HR=11.61, p<0.001) had significantly worse prognosis when compared to those diagnosed with RCC. Surgical resection was observed to improve overall survival (HR=0.36, p=0.001) while no difference in survival was observed with radiotherapy (p=0.837). Conclusion: Pediatric non-Wilms renal tumors are composed mainly of RCC, CCS, and MRT. Younger patients and those diagnosed with RCC have improved survival while a diagnosis of MRT portends a worse prognosis. Surgical extirpation is the only identifiable treatment modality that significantly improves survival.