Characteristics and outcomes of preoperatively treated patients with anaplastic Wilms tumors registered in the UK SIOP-WT-2001 and IMPORT study cohorts (2002-2020).

Anaplasia is an unfavorable feature in Wilms tumor (WT), and it is classified as focal (focal anaplastic Wilms tumor [FAWT]) or diffuse (diffuse anaplastic Wilms tumor [DAWT]). This study reports the outcomes of patients with FAWT and DAWT who were, for the first time, treated differently. Patients with FAWT received less intensive treatment, and their outcomes were comparable to the outcomes of patients with identically treated nonanaplastic WT. Patients with stage I DAWT also had good outcomes when they were treated without radiotherapy, whereas patients with stage II to V DAWT had poor outcomes despite more intensive treatment.