ESTRO 2024 - Abstract Book

S1159

Clinical - Haematology

ESTRO 2024

Exposure of breast tissue in modern radiotherapy for lymphoma: a systematic review

Hannah C Chamberlin 1 , George Ntentas 2,3,4 , David J Cutter 2,5 , Richard Cowan 6,7 , Sacha J Howell 8,9 , Sue Astley 10,11 , Christina Hague 6 , John Radford 6 , Eliana M Vasquez Osorio 1 , Marianne C Aznar 1 1 University of Manchester, Radiotherapy Related Research Group, Manchester, United Kingdom. 2 University of Oxford, Nuffield Department of Population Health, Oxford, United Kingdom. 3 Guy's and St Thomas' NHS Foundation Trust, Department of Medical Physics, London, United Kingdom. 4 King's College London, School of Biomedical Engineering & Imaging Sciences, London, United Kingdom. 5 Oxford University Hospitals NHS Foundation Trust, Oxford Cancer and Haematology Centre, Oxford, United Kingdom. 6 The Christie NHS Foundation Trust, Department of Clinical Oncology, Manchester, United Kingdom. 7 The University of Manchester, Division of Cancer Sciences, Manchester, United Kingdom. 8 University of Manchester, Division of Cancer Sciences, Manchester, United Kingdom. 9 The Christie NHS Foundation Trust, Manchester Academic Health Science Centre, Manchester, United Kingdom. 10 University of Manchester, Division of Informatics, Manchester, United Kingdom. 11 NIHR Manchester Biomedical Research Centre, Manchester Academic Health Science Centre, Manchester, United Kingdom

Purpose/Objective:

Radiotherapy (RT) for Hodgkin lymphoma frequently results in exposure of breast tissue, which increases the risk of radiotherapy-induced breast cancer (RIBC) in young women [1]. However, the link between breast dose and RIBC is poorly understood, and current RIBC risk models rely on the field and prescribed dose as surrogates [2]. RIBC risk modelling using individualised measures of breast doses would enable treatment decisions to be made considering breast cancer risk, and personalise subsequent breast screening to individual RIBC risk [3]. However, this would require consistent reporting of dose in large patient cohorts. The aim of this systematic review was to determine the most common metrics used to describe dose to the breast from modern radiotherapy techniques.

Material/Methods:

Embase and Medline were searched for papers published between 01/2000 and 05/2023 with the search terms (lymphoma AND dos* AND (radiation OR radiation therapy OR radiotherapy) AND breast). Quantitative measures of breast dose (VxGy = volume of breast tissue receiving x Gray (Gy) or more, Dx: Dose received by x% or x cm 3 of breast tissue) and prescription dose were extracted. Qualitative variables collected included: publication year, breast contouring technique/guidelines stated, number of female patient plans, target volume contouring approach (i.e., involved node RT (INRT)), arm positioning, position on table, and whether the mediastinum and/or axilla was a target. Frequency of reporting for each breast dose metric across all papers was calculated. Doses were pooled across papers and associations between breast dose and qualitative variables were investigated using Mann-U Whitney tests for significance. For breast doses reported to individual breasts, we calculated the average as an estimate of the combined breast dose (referred to as ‘both (calc)’) for use in analysis.

Results:

After examination of 1797 search results, 57 papers were included in the quantitative analysis. The most commonly reported breast dose metrics were mean breast dose (MBD) (Gy), V5Gy (%) and V10Gy (%). We examined these metrics in Gy and in percentage of prescription dose when reported (%pres) (Figure 1). 23 papers reported MBD for