Radiation target nomenclature for lymphoma trials: consensus recommendations from the National Clinical Trials Network groups

Contemporary lymphoma radiation target volumes that rely on post-systemic therapy imaging do not have standardised nomenclature. A forum of radiation oncology lymphoma leaders from the National Clinical Trials Network groups (NRG Oncology, Children's Oncology Group, SWOG Cancer Research Network, Alliance for Clinical Trials in Oncology, Eastern Cooperative Oncology Group–American College of Radiology Imaging Network Cancer Research Group, and the Canadian Cancer Trials Group) was convened and established standardised nomenclature for these volumes in the autumn of 2024. Involved-site radiotherapy includes the full cranial–caudal extent of prechemotherapy disease and takes into account axial anatomical changes only. Residual site radiotherapy targets only the postchemotherapy CT-anatomical mass. PET-directed radiotherapy exclusively targets PET-positive disease and includes three types: PET-directed involved site radiotherapy using the superior–inferior aspect of prechemotherapy involved disease sites that remain PET-avid on post-treatment imaging; PET-directed residual site radiotherapy using only the postchemotherapy CT-anatomical residual mass that contains the PET-avid lesion on post-treatment imaging, without excluding sites that had complete metabolic response; and PET-directed residual PET radiotherapy using only the PET-avid focus, irrespective of the corresponding adjacent non-PET-avid CT-anatomical disease surrounding it.