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

Saifi O, Pinnix CC, Ballas LK, Kelsey CR, Milgrom SA, Terezakis SA, Figura NB, Parikh RR, Grecula JC, Flampouri S, Ha CS, Lo AC, Plastaras JP, Hodgson DC, Hoppe BS. Radiation target nomenclature for lymphoma trials: consensus recommendations from the National Clinical Trials Network groups. Lancet Haematol. 2024 Dec;11(12):e951-e958. doi: 10.1016/S2352-3026(24)00276-X. Epub 2024 Sep 30. PMID: 39362223; PMCID: PMC11635836.

Contemporary lymphoma radiation (RT) target volumes that rely on post-systemic therapy imaging lack standardized nomenclature. A forum of radiation oncology lymphoma leaders from NCTN groups (NRG, COG, SWOG, ALLIANCE, ECOG-ACRIN, CCTG) was convened and established standardized nomenclature for these volumes. ISRT includes the full cranial-caudal extent of pre-chemo disease and takes into account axial anatomical changes only. Residual site radiotherapy (RSRT) targets only the post-chemo CT-anatomical mass. Positron emission tomography (PET)-directed radiotherapy (PD-RT) exclusively targets PET-positive disease and includes 3 types. PET-directed involved site radiotherapy (pISRT) includes the superior-inferior aspect of the pre-chemo involved disease site(s) that remain(s) PET-avid on post-treatment imaging. PET-directed residual site radiotherapy (pRSRT) includes only the post-chemo CT-anatomical residual mass that contains the PET-avid lesion on post-treatment imaging, without including sites that achieved complete metabolic response. PET-directed residual PET radiotherapy (pRPRT) includes only the PET-avid focus, irrespective of the corresponding adjacent non-PET-avid CT-anatomical disease surrounding it.