Many pediatric cancers have very poor overall survival rates once they relapse or if they do not respond to initial standard treatments. Radiotherapy plays an important role in the treatment of these cancers. However, if the cancer has metastasized to many sites, external beam radiotherapy becomes impracticable and too harmful to healthy body tissues. CLR 131 by Cellectar Biosciences, is a radio iodinated therapeutic that selectively delivers radiation to malignant tumor cells, thus minimizing radiation exposure to normal tissues. It consists of a cancer-targeted small-molecule compound radiolabeled with isotope iodine-131. CLR 131 has demonstrated tumor selective uptake and therapeutic efficacy in various pediatric cancers. We talked to Dr. Mario Otto, University of Wisconsin School of Medicine and Public Health and Dr. Daniel Morgenstern, SickKids about use of CLR 131 in pediatric cancers, status on the clinical trials and scope of targeted radiotherapeutics in pediatric cancers.