Vujanic GM, D'Hooghe E, Graf N, et al. - The aim of the study was to evaluate whether a subset of regressive type Wilms tumor (WT) (RT-WTs)(67-99% chemotherapy-induced changes - CIC) showing an exceptionally good response to preoperative chemotherapy had comparably excellent survivals as Completely necrotic WTs (CN-WTs), and to establish a cut-off point of CIC that could define this subset. The study included 2,117 patients with unilateral, nonanaplastic WTs from the UK-CCLG and GPOH-WT studies (2001-2020) treated according to the SIOP-WT-2001 protocol. Patients with STN-WT96-99 share the same excellent EFS and OS as patients with CN-WTs, and although this was achieved by more treatment for patients with STN-WT96-99 than for patients with CN-WT, reduction in postoperative treatment of these patients may be justified.