S2440
Physics - Radiomics, functional and biological imaging, and outcome prediction
ESTRO 2026
radiotherapy. Building on a model previously applied to lung cancer [1], the present study evaluated the ability of FDG-PET–derived effective radiosensitivity ( α eff) to predict target response very early during treatment and explored its applicability to head and neck cancer (HNC), as a step toward validation across tumour sites. Material/Methods: Baseline and in-treatment FDG-PET/CT scans were obtained for 151 patients of the ARTFORCE trial [2], including 80 treated with FDG-PET–guided dose painting (DP; 64–84 Gy) and 71 with standard radiotherapy (ST; 70 Gy), with 26 local failures overall (15 ST, 11 DP). The operational parameter α eff, which quantifies the effective radiosensitivity by relating changes in FDG-PET uptake between baseline and in- treatment scans to the planned dose scaled by the number of fractions until the second acquisition, was calculated at voxel level. Voxel-wise mapping was performed in RayStation using deformable registration.Fig. 1 illustrates an example of the α eff distribution and regions within the primary gross tumour volume (GTVp) with positive and negative α eff values. The mean ( ᾱ eff) and the fraction of α eff < 0 (f α eff) were extracted and used as single-feature predictors of local control through receiver operating characteristic (ROC) analysis. The area under the curve (AUC), sensitivity, and specificity were estimated with 95% bootstrap confidence intervals to assess discriminative performance.
Conclusion: FDG-PET–derived α ₑ ff predicted local control for HNC patients imaged during week 2, showing the highest performance in the DP arm, which appears to drive the overall effect, as no predictive value was observed in the ST arm. These findings suggest that a wider dose range may increase the α ₑ ff sensitivity to treatment-induced metabolic changes, warranting further investigation. Extending previous findings in lung cancer, this study further shows the potential of α ₑ ff as a biologically informed biomarker for individualized radiotherapy in HNC. References: 1.Toma-Dasu I, Uhrdin J, Lazzeroni M et al. Evaluating tumour response of non-small cell lung cancer patients with ¹⁸ F-fludeoxyglucose positron emission tomography: potential for treatment individualization. Int J Radiat Oncol Biol Phys. 2015;91(2):376-384. doi:10.1016/j.ijrobp.2014.10.0122.de Leeuw ALMP, Giralt J, Tao Y et al. A multicentric randomized controlled phase III trial of adaptive and ¹⁸ F-FDG-PET- guided dose-redistribution in locally advanced head and neck squamous cell carcinoma (ARTFORCE). Radiother Oncol. 2024;196:110281. doi:10.1016/j.radonc.2024.110281 Keywords: FDG-PET, radiosensitivity, response prediction Atrial fibrillation risk in patients with esophageal cancer after tri-modality treatment: Development and validation of a multicenter prediction model Iris A.G. Holtmaat 1 , Mark L. Frederiks 1 , Bas P.L. Wijnhoven 2 , Ewoud Schuit 3 , Peter S.N. van Rossum 4,5 , Hanneke W.M. van Laarhoven 5,6 , Gert J. Meijer 7 , Stella Mook 7 , Joost J. Nuyttens 8 , Heidi Rütten 9 , Bastiaan R. Klarenbeek 10 , Mariska D. den Hartogh 11 , Meindert Sosef 12 , Boudewijn van Etten 13 , Rob H.A. Verhoeven 14 , Johannes A. Langendijk 1 , Maaike Berbée 15 , Christina T. Muijs 1 1 Department of Radiation Oncology, University Medical Center Groningen, Groningen, Netherlands. 2 Department of Surgery, Erasmus MC Cancer Institute, Rotterdam, Netherlands. 3 Department of Epidemiology & Health Economics, Julius Center for Health Sciences and Primary Care, University Medical Proffered Paper 2281
Results: ROC analysis showed high predictive performance for patients imaged during the second week, with the highest performance achieved in the DP cohort, where, for GTVp, the ᾱ eff-AUC was 0.87 (p < 0.001) (Fig. 2A) and f α eff -AUC was 0.84 (p <0.001) (Fig. 2B). For the whole cohort, the performance was lower: ᾱ eff-AUC was 0.68 (p < 0.001) and f α eff -AUC was 0.61 (p = 0.056). For patients imaged in week 2 across all arms, ᾱ eff-AUC was 0.74 (p < 0.001) and f α eff-AUC was 0.71 (p = 0.006). For the ST arm, no predictive value was observed.
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