Pd37-03 does Neoadjuvant Chemotherapy Reduce the Complexity of Wilms Tumor? An Analysis Using the Nephrometry Score

Abstract

Per the Children's Oncology Group (COG) protocols, partial nephrectomy (PN) for Wilms tumor (WT) is reserved for bilateral tumors or lesions in solitary kidneys. Furthermore, most WTs are large masses that would not be amenable to partial nephrectomy. Unlike COG, the Societe Internationale d'Oncologie Pediatrique (SIOP) offers neoadjuvant chemotherapy (NAC) prior to surgical resection, allowing for tumor shrinkage. The Nephrometry score (NS) is a tool that was developed to assess the complexity of renal cell carcinoma, and thus the feasibility of partial nephrectomy. It relies on morphological features of tumors seen on cross-sectional imaging. The NS was however developed for renal cell carcinoma. Only one study to date has assessed Wilms tumors using the NS, showing that most are highly complex lesions not amenable to (PN). The goal of our study is to assess if NAC decreases the complexity of Wilms tumor using the NS.METHODS: We retrospectively identified patients with WT at our institution who received NAC (according to COG protocols). Preand post-treatment tumor volumes and NS were calculated by a single radiologist. For bilateral or multifocal tumors, the score was calculated for the most complex mass. NS was broken down into low, intermediate and high complexity groups. Rates of PN were stratified by NS score and by pre-operative variables. Statistical differences were assessed using paired t-tests and chi square tests.RESULTS: 54 patients were identified. The median pre-and post-treatment tumor volumes were 499 and 90 cm3, respectively (p<0.0001). Before NAC, NS was considered low, intermediate and high in 3.7%, 13% and 83.3% of patients, respectively. After NAC, the NS score was low, intermediate and high in 11.1%, 25.9% and 63% of patients. Fourteen tumors (26%) had their complexity downgraded. Overall rates of PN were 35% (n[19). There were statistically significant higher rates of PN for tumors with a low NS (83%) vs intermediate (64.3%) and high (14.7%) scores (p<0.0001). Among pre-operative variables such as age, sex, race, ethnicity, syndromic Wilms and stage, only female sex was statistically associated with higher rates of downgrading after NAC (36% vs 9.5% of males, p[0.028).CONCLUSIONS: The majority of WT are complex masses. Our data shows that NAC can reduce tumor complexity in 26% of cases, with more than half the patients with low or intermediate complexity WT undergoing successful PN. Further studies are needed to identify which patients with unilateral non-syndromic WT could benefit from NAC with the goal of nephron-sparing surgery.