S832
Clinical - Lung
ESTRO 2026
Digital Poster 4149 Manual coronary artery segmentation on 4- dimensional radiotherapy planning scans: old dogs can learn new tricks! Andrew IP Walker 1 , Cathryn Crockett 1 , Jonathan McAleese 1 , Claire Harrison 1 , Jolyne O’Hare 1 , Nicola Hill 1 , Conor K McGarry 1,2 , Frances K Duane 3,4 , Gerard M Walls 1,2 1 Cancer Centre Belfast City Hospital, Belfast Health & Social Care Trust, Belfast, United Kingdom. 2 Johnston Cancer Research Centre, Queen’s University Belfast, Belfast, United Kingdom. 3 St. Luke's Radiation Oncology Network, St. Luke's Hospital, Dublin, Ireland. 4 Trinity St. James's Cancer Institute, Trinity College Dublin, Dublin, Ireland Purpose/Objective: Incidental dose to the coronary arteries (CAs) is associated with cardiac events after thoracic radiotherapy, along with classic cardiovascular risk factors1,2, yet the CAs have not been adopted as organs-of-interest widely in clinical practice3. Contouring the CAs on 4DCT planning scans is anecdotally perceived to be difficult and time- consuming and conventional radiotherapy training curricula do not typically include the CAs. The CAs are not commonly included in auto-segmentation packages, although when they do in future, clinicians will be required to provide supervision. In this study, manual CA segmentation was assessed qualitatively (geometry) and quantitatively (dosimetry). Material/Methods: Five consultant radiation oncologists without prior experience delineated the left anterior descending (LAD), right (RCA) and left circumflex (LCX) CAs on the average image projection of 5 patients treated with VMAT for non-small cell lung cancer scanned with 4DCT. A European CA atlas4 was provided for this procedure without any further training, and clinicians recorded the time taken. Segmentations were evaluated using an abbreviated qualitative scale (‘Acceptable’, ‘Minor Edits’, ‘Major Edits’) by an expert in CA contouring, and dosimetric comparison was made with reference delineations for the mean and maximum doses, and the volume receiving ≥ 15Gy. Results: The quality of CA contouring was high, with 57/75 arteries (76%) rated as ‘Acceptable’, 15/75 (20%), ‘Minor edits’ and 3/75 (4%) ‘Major edits’. Median time required per artery was 2 minutes (LAD 121.0s, RCA 120.0s, LCX 125.0s). The overall median absolute volume difference compared with reference contours was -0.1cc (IQR -1.1–1.8), and per artery, LAD (-0.9cc), RCA (+1.1cc), LCX (+0.9cc). The median absolute Dmax difference was -0.1Gy (IQR -3.6–0.23), per artery, LAD (- 3.5Gy), RCA (-0.1Gy), LCX (-0.6Gy). The median absolute
Conclusion: Higher radiation doses to the left atrium, superior vena cava, and right ventricle were independently associated with worse OS after SBRT for central and ultracentral lung tumors, underscoring the importance of cardiac-substructure–specific dose constraints in SBRT planning. Moreover, a clear trend toward reduced survival with higher doses to the base of the heart underscores the importance of this region as a potential target for future dose-sparing strategies. References: 1. McWilliam A, Kennedy J, Hodgson C, Vasquez Osorio E, Faivre-Finn C, van Herk M. Radiation dose to heart base linked with poorer survival in lung cancer patients. Eur J Cancer. 2017 Nov 1;85:106–13. Keywords: SBRT, cardiac toxicity, base of the heart
Digital Poster 4118
Analysis of 58 patients referred to MRI-guided stereotactic radiation therapy for lung tumors Kukka Heiskala 1 , Laura Tuomikoski 1 , Maria Faltinova 2 , Anu Anttonen 1 1 Comprehensive Cancer Center, Helsinki University Hospital (HUS), Helsinki, Finland. 2 University of Helsinki, Helsinki University Hospital (HUS), Helsinki, Finland
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