The article discusses a method of radiotherapy developed by researchers at French nanomedicine firm Nanobiotix in which the radiation dose in the tumor can be increased without increasing the dose in healthy tissue. Topics include intra-tumour delivery of hafnium dioxide (HfO2) nanoparticles, comments from Nanobiotix chief executive officer (CEO) Laurent Levy on the potential uses for the company's method, and the safety and efficacy of HfO2 nanoparticles.