ESTRO 2025 - Abstract Book

S1091

Clinical – Head & neck

ESTRO 2025

University of Medical Sciences, Poznan, Poland. 10 Radiotherapy Department II, Greater Poland Cancer Centre, Poznan, Poland. 11 Department of Nuclear Medicine, LMU University Hospital, Munich, Germany. 12 Department of Radiation Oncology, German Oncology Center, Limassol, Cyprus. 13 Bavarian Cancer Research Center (BZKF), Partner Site Munich, Munich, Germany. 14 German Cancer consortium (DKTK), Partner Site Munich, Munich, Germany. 15 Department of Nuclear Medicine, Greater Poland Cancer Centre, Poznan, Germany. 16 Department of Nuclear Medicine, Faculty of Medicine and University Hospital Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany. 17 OncoRay – National Center for Radiation Research in Oncology, University Hospital Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany. 18 Division of Radiooncology/Radiobiology, German Cancer Research Center (DKFZ), Heidelberg, Germany. 19 German Cancer Consortium (DKTK), partner site Dresden, Germany, and German Cancer Research Center (DKFZ) Heidelberg, Dresden, Germany. 20 Department of Radiation Oncology, Charite – Universitätsmedizin Berlin, Charite, Germany. 21 German Cancer Consortium (DKTK), German Cancer Research Center (DKFZ) Heidelberg, Dresden, Germany. 22 German Cancer Consortium (DKTK), partner site Berlin, a partnership between DKFZ and Charité, Berlin, Germany. 23 Department of Nuclear Medicine, University Hospital Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany. 24 Institute of Radiopharmaceutical Cancer Research, , Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany Purpose/Objective: In the past, FDG-PET scans were used to determine prognosis by using well established parameters like metabolic tumor volume (MTV), standardized uptake values (SUV max ) and total lesion glycolysis (TLG). Asphericity (ASP) is a new parameter, used as a measure for quantifying the fractional deviation of actual tumor surface area from that of an isovolumetric sphere. In smaller patient cohorts, it has already demonstrated potential prognostic value. In this large multicenter retrospective study, we investigated the prognostic value of ASP in patients with head and neck squamous cell carcinoma (HNSCC). Material/Methods: We analyzed 1104 patients with locally advanced HNSCC from 8 international treatment centers. All patients received FDG-PET-scans as part of their staging. FDG-PET-scans were analyzed for MTV, SUV max , TLG, and ASP. All patients received curative intended radiotherapy or chemoradiotherapy. Primary endpoints were loco-regional control (LCR) and overall survival (OS). For risk stratification, multivariate and univariate Cox regression analyses were evaluated for LCR and OS. For ASP, to differentiate between low risk and high risk groups, a cutoff was calculated by minimizing the p-value in univariate Cox regression. ASP was additionally combined with MTV – the best-established quantitative PET parameter. Results: ASP as an individual marker correlated only marginally with known PET parameters including MTV, SUV max , and TLG. For LCR, less than 19% ASP showed significantly better outcomes (p <0.001) and for OS an ASP below 16,8% indicated significantly better outcomes (p<0.001). In multivariate Cox regression, the well-established parameters were not significantly correlated for LCR and OS, except for ASP and MTV (p<0.021/0.001 and p<0.001). ASP and MTV were binarized and combined for risk stratification. The prognostic value of the combination was compared to the prognostic value of individual parameter. For LCR and OS, ASP with MTV as binarized parameters showed significantly better risk stratification, compared to MTV (p<0.012/0.001) alone and ASP regarding to OS (p<0.001).

Conclusion: In this retrospective analysis, ASP was shown as valuable independent prognostic parameter in head and neck squamous cell carcinoma patients. It's risk stratification was improved significantly when combined with MTV.

Keywords: HNSCC, FDG-PET-CT, Asphericity