Bonvalot S, et al. - Among patients with locally advanced soft-tissue sarcoma, researchers assessed the safety as well as the effectiveness of the hafnium oxide nanoparticle NBTXR3 activated by radiotherapy vs radiotherapy alone as a pre-operative treatment in the Act.In.Sarc, a phase 2-3 randomized, multicenter, open-label, international trial. In the NBTXR3 group and in the radiotherapy alone group, a pathological complete response was observed in 14 of 87 patients and in seven of 89 patients, respectively. Postoperative wound complication was identified as the most common grade 3–4 treatment-emergent adverse event that occurred in both treatment groups, seen in eight of 89 patients and in eight of 90 in the NBTXR3 group and in the radiotherapy alone group, respectively. In the NBTXR3 group and in the radiotherapy alone group, serious adverse events occurred in 35 of 89 patients and in 27 of 90 patients, respectively. There were no treatment-related deaths. In this study, the mode of action of this novel class of radioenhancer received validation.