S521
Clinical - Haemotology
ESTRO 2026
1 Division of Cancer Sciences, University of Manchester, Manchester, United Kingdom. 2 Clinical Oncology, The Christie NHS Foundation Trust, Manchester, United Kingdom. 3 Science and Innovation, The Alan Turing Institute, London, United Kingdom. 4 Medical Oncology, The Christie NHS Foundation Trust, Manchester, United Kingdom Purpose/Objective: Early-stage Hodgkin Lymphoma (HL) has an excellent prognosis, creating a large population of long-term survivors. Improvements in radiotherapy delivery and combined-modality therapy have reduced field sizes and exposure of organs-of-interest (OOIs), potentiallyreducing breast dose [1]. However, all young women receiving mediastinal radiotherapy are currently referred to high-risk breast cancer screening irrespective of breast dose. We evaluated breast and other mediastinal OOI doses in young women treated with three-dimensional conformal radiotherapy (3DCRT) over sixteen years at a single institution. Material/Methods: Women under 36 years of age who received mediastinal RT between 2005-2021 were included. OOI contours were generated for right, left, and combinedbreasts, combined lungs, oesophagus, thyroid, heart, and cardiac substructures (CS; right and left ventricles and atria) using Limbus AI (v1.9.0-B1). Mean dose for all OOI was calculated. Moreover, for breast, V4Gy, V10Gy, V15Gy, and V30Gy (% and cm^3) were calculated to investigate low-, mid-, and high- dose trends. Time trends were investigated using Spearman’s rank coefficient ( ρ ) and ordinary least squares (OLS) linear regression. Results: 112 patients aged 13-35 (median 23.5 years) received 3DCRT; 103 with AP/PA fields, and 9 with non-standard fields (Table 1). Median population combined mean breast dose was 1.93Gy (IQR: 1.0-3.2 Gy). No statistically significant mean dose time trends or decrease in breast dose metrics were observed (Figure 1). Among other OOIs, only lung showed a slight decrease (OLS p=0.03, Spearman’s p=0.1). Inter-patient variation was high across all OOIs (OLS R^2<0.03). Over half of breasts (combined, right, left) received mean dose <2Gy. Median combined-breast dose metrics were V4Gy 7.5% (138cm^3), V10Gy 5.5% (95cm^3), V15Gy 4.6% (78cm^3), and V30Gy 1.6% (22cm^3). Median doses to other OOIs are reported in Figure 1.
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