ESTRO 2023 - Abstract Book

S763

Monday 15 May 2023

ESTRO 2023

With the availability of new radiation techniques, image guidance and adapted fractionation schemes, the use of re irradiation (re-RT) for different sites is increasing, although prospective evidence is still scarce and a standardized nomenclature is lacking. We hereby present the consensus definition of re-RT and recommendations to harmonize reporting for clinical studies, prepared in the scope of the EORTC RP-2011 ReCare study. Materials and Methods This consensus was developed during the preparation of the prospective observational ReCare cohort within the ESTRO EORTC E2-RADIatE project, aiming to gather real-world data on safety and efficacy of high-dose re-RT to derive evidence based dose/fractionation settings for re-RT. The 17 panellists represent experts from different professional backgrounds (e.g., radiation oncologists, clinical oncologists, medical physicists) and have been selected based on their publication track record on re-RT. The consensus is based on a systematic review and an adapted Delphi process. Results Fourteen potential characteristics of re-RT were collated and grouped into categories (irradiated region, prescription dose, time interval between treatments and degree of overlap). We reached consensus on: 1) a new course of RT, 2) overlap of irradiated volumes, 3) toxicity concerns from cumulative doses. The following definition of re-RT was derived: “Re-RT is a new course of RT either to a previously irradiated volume (irrespective of concerns of toxicity) or where the cumulative dose raises concerns of toxicity”. To distinguish other forms of repetitive RT, two additional terms were introduced (Figure 1). Finally, a hierarchical question-based decision tree was built to help classify patients selected for repetitive RT (Figure 2).

Figure 1: Examples for scenarios of re-RT and re-treatments with RT.

Figure 2: Decision tree for the definition of re-RT and classification for scenarios with RT re-treatment. Q1: Is there a