The development of novel molecular tools to accurately measure response to therapy is one of the major challenges in clinical cancer research. Based on recent findings that circulating miRNA molecules can serve as biomarkers for cancer diagnosis and prognosis, we hypothesize that levels of circulating miRNAs can also be applied to monitor response to treatment. In this project, we propose to measure circulating miRNAs in serum of neuroblastoma patients pre- and post-treatment. Our goal is to determine a miRNA signature that is predictive for treatment response in high-risk neuroblastoma patients.