The researchers analysed the records of 548 children with a suspected kidney cancer treated in the UK and Republic of Ireland who took part in an international clinical trial (SIOP WT 2001) between 2002-2011. During this trial, all children in the UK/ROI were recommended to have a biopsy before starting chemotherapy. In other countries, chemotherapy is usually started without a biopsy since nine times out of ten, a kidney tumour in a young child is a type of cancer called Wilms tumour and the diagnosis is confirmed when the affected kidney is removed 4-6 weeks later. Giving chemotherapy before surgery to remove a kidney affected by Wilms tumour makes surgery less risky. However, chemotherapy is not needed for some non-Wilms tumours.