ESTRO 2025 - Abstract Book

S1409

Clinical - Lung

ESTRO 2025

References: [1] Beekman C, Withrow JD, Correa Alfonso CM, Pathak SP, Dawson RJ, Carrasco-Rojas N, et al. A stochastic model of blood flow to calculate blood dose during radiotherapy. Phys Med Biol 2023;68:225007 [2] Campbell BA, Callahan J, Bressel M, Simoens N, Everitt S, Hofman MS, et al. Distribution Atlas of Proliferating Bone Marrow in Non-Small Cell Lung Cancer Patients Measured by FLT-PET/CT Imaging, With Potential Applicability in Radiation Therapy Planning. International Journal of Radiation Oncology*Biology*Physics 2015;92:1035–43. This study was funded by NIH/NCI (grants P01 CA261669, R01 CA248901) and by the Polish National Agency for Academic Exchange/National Science Centre Poland (grant 2020/39/O/NZ5/01696)

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Digital Poster Correlation of the heart–tumour geometric relationship with heart dose and PTV coverage in lung cancer radiotherapy across multiple planning solutions Fereshteh Gholami 1 , Aimee Gannon 2 , Glenn Whitten 2 , Denise Irvine 2 , Gerard M.Walls 1,2 , Conor K.McGarry 1,2 1 Patrick G. Johnston Centre for Cancer Research, Queen’s University of Belfast, Belfast, United Kingdom. 2 Cancer Centre Belfast City Hospital, Belfast Health & Social Care Trust, Belfast, United Kingdom Purpose/Objective: Radiotherapy is a curative-intent treatment for patients with lung cancer, however the risk of cardiotoxicity despite technological improvements means refinement of cardiac dose assessment is required. This study explores the impact of the geometric relationship between planning target volume (PTV) and the heart for three planning solutions: 3D-conformal radiotherapy (3DCRT), intensity-modulated radiotherapy (IMRT), and volume modulated arc therapy (VMAT). Material/Methods: Retrospective analysis of 406 non-small cell lung cancer (IRAS 293181), treated with 3DCRT (n=100), IMRT (n=84) or VMAT (n=222). Dose calculations for 3DCRT cases were originally performed using pencil beam algorithm, IMRT, using collapsed cone algorithm, and VMAT, using the anisotropic analytical algorithm (AAA). All cases were recalculated with AAA algorithm (V16.1.4) in Eclipse treatment planning system. Dosimetric analysis focused on mean heart dose (MHD) and PTV coverage at D95% (percentage of prescribed dose received by 95% of PTV) and D99%. Geometric parameters, including the 3D distance between centre of heart and PTV ( ctc Heart-PTV ), overlap volume between heart and PTV (OVHP) [1] , and PTV Volume (V PTV ) were extracted using dicompylercore and pydicom python libraries [2][3]. Pearson values were used to examine the strength of the correlation, defined as weak (|r|<0.3), moderate (0.4≤|r|<0.7), and strong (|r|≥0.7). Kruskal-Wallis and Mann-Whitney U tests to evaluate statistical significance. Results: Significant dose differences were observed between radiotherapy techniques (p<0.001 for MHD, D95, and D99, Table 1). MHD for VMAT (6.01 Gy [0.09–28.49]) was significantly lower compared to IMRT (8.53 Gy [0.22–29.71], p = 0.001) and 3DCRT (7.63 Gy [0.34–25.90], p = 0.004). However, PTV D95% was notably higher for 3DCRT. OVHP had a strong positive correlation with MHD for all techniques. V PTV showed a moderate correlation, with greater influence on MHD than ctcHeart-PTV. A moderate negative correlation between OVHP and D95 for 3DCRT suggested reduced PTV coverage with increased overlap, but this was not evident for IMRT or VMAT. Correlation between ctc Heart-PTV and MHD/D95 was weak across all techniques (Figure 1).