S766
Clinical - Lung
ESTRO 2026
Mini-Oral 916
is accurate, most centres (80%, 12/15) evaluate cumulative dose using 3D registration. In cases of poor registration, 67%, (10/15) use the ‘best possible’ registration, with 33% (5/15) including manual point dose calculations. In the absence of prior DICOM data, 27% (4/15) simulate the previous radiotherapy on the current CT, while 20% (3/15) rely on manual point dose calculations. Accounting for normal tissue recovery, 87% (13/15) apply dose discounts to prior radiotherapy, while 47% (7/15) increase OAR dose guidance. All centres reported using organ-specific dose discounts, although 53% (8/15) don’t apply discounts to certain organs. The minimum interval for applying dose discount ranged from 3-12 months in 67% (10/15) of centres, with 27% (4/15) using time- dependant tissue recovery models(2). Cumulative dose to the spinal cord (80%, 12/15), brachial plexus (73%, 11/15) and esophagus (60%, 9/15) are most likely to influence a plan compromise. Conversely, cumulative dose to the lungs (47%, 7/15), ribs (67%, 10/15) and skin (53%, 8/15) were unlikely to prompt a plan compromise. Concerning normal lung tissue, 40% (6/15) were likely to de-escalate a plan based on excess cumulative point dose (Type 1 reirradiation(3)) rather than cumulative total lung dose (Type 2 reirradiation (3)), (13%, 2/15). Where required, common plan modifications included altered dose/fractionation (93%, 14/15), compromised target coverage (93%, 14/15), reduced prescription dose (87%, 13/15), omission of reirradiation (73%, 11/15), exceeding standard DVCs (73%, 11/15) and differential dose prescription to target volumes (60%, 9/15). Conclusion: While centres agree on the broad principles for safely delivering thoracic reirradiation, practice variability across Ontario highlights the need for consensus- based guidelines and further research to support clinical decision-making. References: 1. Nieder C, Andratschke NH, Grosu AL. Increasing frequency of reirradiation studies in radiation oncology: systematic review of highly cited articles. American journal of cancer research. 2013;3(2):152. 2. Paradis KC, Mayo C, Owen D, Spratt DE, Hearn J, Rosen B, et al. The Special Medical Physics Consult Process for Reirradiation Patients. Adv Radiat Oncol. 2019;4(4):559-65. 3. Andratschke N, Willmann J, Appelt AL, Alyamani N, Balermpas P, Baumert BG, et al. European Society for Radiotherapy and Oncology and European Organisation for Research and Treatment of Cancer consensus on re-irradiation: definition, reporting, and clinical decision making. The Lancet Oncology. 2022;23(10):e469-e78. Keywords: Reirradiation, practice patterns, QA
Blood biomarkers in NSCLC stage III: results from the Austrian radio-oncologicaL Lung cancer STudy Association Registry (ALLSTAR) Alexandra Hochreiter 1 , Markus Stana 1 , Marisa Klebermass 2 , Elvis Ruznic 1 , Brigitte Langer 2 , Brane Grambozov 1 , Petra Feurstein 2 , Josef Karner 1 , Barbara Zellinger 3 , Martin Heilmann 4 , Heidi Stranzl 5 , Danijela Minasch 6 , Karoline Kirchhammer 7 , Thomas Kann 8 , Ayurzana Purevdorj 9 , Barbara Böhmer-Breitfelder 10 , Georg Gruber 11 , Karin Dieckmann 4 , Falk Röder 1 , Franz Zehentmayr 1 1 Department of Radiation Oncology, Paracelsus Medical University, Salzburg, Austria. 2 Department of Radiation Oncology, Klinikum Ottakring, Vienna, Austria. 3 Department of Pathology, Paracelsus Medical University, Salzburg, Austria. 4 Department of Radiation Oncology, Comprehensive Cancer Centre, Medical University Vienna, Vienna, Austria. 5 Department of Radiation Oncology, Comprehensive Cancer Centre, Medical University Graz, Graz, Austria. 6 Department of Radiation Oncology, Comprehensive Cancer Centre, Medical University Innsbruck, Innsbruck, Austria. 7 Department of Radiation Oncology, Klinikum Klagenfurt, Klagenfurt, Austria. 8 Department of Radiation Oncology, Klinik Favoriten, Vienna, Austria. 9 Department of Radiation Oncology, Klinikum Hietzing- Rosenhügel, Vienna, Austria. 10 Department of Radiation Oncology, Medical University Krems, Krems, Austria. 11 Department of Radiation Oncology, Ordensklinikum Linz, Linz, Austria Purpose/Objective: There is a need for predictive/prognostic biomarkers in order to identify patients who are likely to benefit from specific treatment strategies and pinpoint those at risk of experiencing severe toxicities. Blood biomarkers of systemic inflammation are inexpensive and easy to collect by means of routine blood sampling. Ratios like the monocytes-lymphocytes-ratio (MLR) and the derived MLR (dMLR) might play a key factor in predicting clinical outcomes in non-small cell lung cancer (NSCLC) and other tumor entities. The aim of this explorative study was to identify potential blood biomarkers of systemic inflammation that might be predictors/prognosticators for locoregional control (LRC) and progression-free survival (PFS) in patients with unresectable NSCLC stage III. Material/Methods: Pre-treatment blood samples of 183 patients from the ALLSTAR cohort with pathologically confirmed unresectable NSCLC stage III with a curative treatment indication (radio-chemotherapy, Durvalumab consolidation) were included. Of these, 112 patients received adjuvant Durvalumab. Ratios of blood biomarkers, particularly MLR and dMLR, were
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