S822
Clinical - Lung
ESTRO 2026
to high-ventilation regions (cyan contour) while maintaining target coverage (red arrow).
support implementation of functional lung-sparing (FLS) planning within the trial. Material/Methods: Consensus-based FLS planning guidelines were established through an iterative process involving an initial test case, multi-centre plan review and a dedicated workshop. A test case with CT ventilation map (CT:VQ, 4DMedical, Australia) and standardised functional lung contours was distributed to centres using Eclipse, RayStation and Monaco systems. Six preliminary site plans were reviewed to assess variability in planning interpretation and implementation. Workshop findings informed refinement of dose-priority, contour definitions, and planning objectives. Following consensus, a credentialling process assessed site readiness. Centres generated standard-of-care (SOC) and FLS benchmark plans prescribing 60 Gy in 30 fractions, per VITaL protocol dose constraints adapted from eviQ radiotherapy guidelines with minor adaptation [2]. Plans were reviewed for compliance, reproducibility, and QA documentation refinement. Results: Initial workshop revealed variation in interpretation of functional contours and dose trade-off between high- and low- functioning lung regions. Consensus led to revised, standardised guidelines, validated through the credentialing workflow. Two sites have successfully completed the radiotherapy planning credentialing process demonstrating full end-to-end implementation of the FLS workflow and consistency between SOC and FLS benchmark plans. Both sites achieved full compliance with all VITaL protocol constraints. Target coverage was maintained for all benchmark plans, with minor iGTV variation between sites that was clinically acceptable. All OAR metrics met protocol limits, including a small oesophagus Dmean variation (~0.8 Gy) for one site, also considered acceptable by clinicians. FLS consistently reduced dose to high-functioning lung regions, with an average reduction of approximately 1 Gy compared to SOC plans across the two credentialed sites without compromising target coverage or increasing other OAR doses. Inter-site variability in functional dose metrics was <10%, confirming reproducibility across systems.
Figure 2: Dosimetric comparison of SOC and FLS benchmark plan across credentialed sites. Conclusion: The VITaL radiotherapy planning credentialing framework provides a reproducible, multi-institutional
QA process enabling consistent, high-quality implementation of functional lung-sparing
radiotherapy within the phase III trial and establishes a model for future multi-centre radiotherapy studies. References: [1] Hegi-Johnson, F., De Ruysscher, D., Keall, P., Hendriks, L., Vinogradskiy, Y., Yamamoto, T., Tahir, B., & Kipritidis, J. (2019). Imaging of regional ventilation: Is CT ventilation imaging the answer? A systematic review of the validation data. Radiotherapy and Oncology, 137, 175– 185. https://doi.org/10.1016/j.radonc.2019.03.010[2] Cancer Institute NSW & eviQ. (2025, August 26). Radiation-induced lung injury (pneumonitis and pulmonary fibrosis) (ID: 1895, v. 5). https://www.eviq.org.au/clinical-resources/side- effect-and-toxicity-management/respiratory/1895- radiation-induced-lung-injury-pneumonitis-an Keywords: Functional Imaging, Healthy lung sparing Correlation between PD-L1 expression and prognosis in early-stage NSCLC treated with stereotactic ablative radiotherapy: a preliminary report Jessica Saddi 1 , David Alberto Santos 1,2 , Elisabetta Bonzano 1 , Andrea Lancia 1 , Salvatore La Mattina 1 , Francesco Agustoni 3,4 , Giulia Galli 3 , Sabrina Borgetto 3 , Giulia Maria Stella 5,4 , Paolo Pedrazzoli 3,4 1 Radiation Oncology, Fondazione IRCCS Policlinico San Matteo, Pavia, Italy. 2 Radiation Oncology, Centro Nacional de Radioterapia, San Salvador, El Salvador. 3 Department of Oncology, Comprehensive Cancer Center, Fondazione IRCCS Policlinico San Matteo, Pavia, Italy. 4 Department of Internal Medicine and Medical Therapeutics, University of Pavia, Pavia, Italy. 5 Department of Medical Sciences and Infective Disease, Unit of Respiratory Disease, Fondazione IRCCS Policlinico San Matteo, Pavia, Italy Digital Poster 3674
Figure1: Standard-of-care and functional lung-sparing plans from a credentialed site, showing reduced dose
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