ESTRO 2025 - Abstract Book

S937

Clinical – Head & neck

ESTRO 2025

Purpose/Objective: The oncological value of stereotactic body radiotherapy (SBRT) in oligometastatic head-and-neck squamous cell carcinoma (HNSCC) is relatively unknown. This study therefore aimed to evaluate the outcomes of pulmonary SBRT in patients with oligometastatic HNSCC and to identify the relationship between the biologically effective dose (BED) and local control. Material/Methods: In a collaborative effort between the German Society for Radiation Oncology (DEGRO) working group "Radiosurgery and Stereotactic Radiotherapy" and Young DEGRO, we conducted an international multicenter cohort study with 16 centers in Germany, Austria, and Switzerland. Oncological outcomes of patients with oligometastatic HNSCC who received SBRT for pulmonary metastases between January 2010 and December 2023 were retrospectively analyzed. The primary endpoint was overall survival (OS), with secondary endpoints including progression-free survival (PFS) and the incidence of local failures. Results: A total of 178 patients with 284 treated lung metastases were analyzed. Metachronous oligorecurrence (113 [63.5%]), de-novo oligometastatic disease (44 [24.7%]), and repeat oligorecurrence (8 [4.5%]) were the most common types of oligometastatic disease at the time of first SBRT. The median BED, assuming an α/β ratio of 10 Gy, was 105 Gy (interquartile range (IQR), 84-113) at the planning target volume (PTV) encompassing isodose, the median PTV inhomogeneity (PTV periphery dose/maximum dose) amounted to 65% (IQR, 65-80). After a median follow-up of 40 months (95% confidence interval (CI), 34-46), the median OS was 33 months (95% CI, 26-40), and the median PFS was 9 months (95% CI, 7-11). Of the 284 lung metastases treated with SBRT, 15 (5.3%) developed local recurrence after a median time of 8 months (IQR, 1-10). The 1-year and 2-year cumulative incidence of local failures was 5.5% (95% CI, 3.1-8.8) and 6.8% (95% CI, 4.1-11.3), respectively. A BED ≥100 Gy at the PTV encompassing isodose was associated with a lower hazard of local failures (subdistribution hazard ratio 0.17; 95% CI, 0.05-0.61; P =.006) in our cohort. The median BED of metastases that progressed after SBRT was 93.6 Gy (range 68.2-112.5). SBRT was well tolerated, with only 0.6% of patients developing acute grade 3 toxicities and 1.4% experiencing chronic grade 3 toxicities. Conclusion: SBRT for pulmonary metastases from oligometastatic HNSCC offers excellent local control with minimal toxicity. If safely achievable, a BED ≥100 Gy at the PTV encompassing isodose is recommended to achieve durable local control. Prospective studies are necessary to identify the optimal patient selection and integration of SBRT with systemic therapies.

Keywords: Oligometastases, SBRT, SABR

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Digital Poster Quality of life and return to work after radiotherapy in young adults with head-and-neck cancer – A bicentric cross-sectional observational study Charlotte Pannenbecker 1 , Clemens Seidel 1,2 , Jiadai Zou 1,2 , Daniel Schnell 3 , Gunnar Wichmann 4,2 , Christoph Becker 5 , Andreas Knopf 5 , Andreas Dietz 4,2 , Anca-Ligia Grosu 3 , Anja Mehnert-Theuerkauf 6,2 , Nils H Nicolay 1,2 , Alexander Rühle 1,2,3 1 Department of Radiation Oncology, University Medical Center Leipzig, Leipzig, Germany. 2 Partner Site Leipzig, Comprehensive Cancer Center Central Germany, Leipzig, Germany. 3 Department of Radiation Oncology, Medical Center – University of Freiburg, Faculty of Medicine, University of Freiburg, German Cancer Consortium (DKTK), partner site DKTK-Freiburg, Freiburg, Germany. 4 Clinic for Otorhinolaryngology and Head and Neck Surgery, Department of Head Medicine and Oral Health, University of Leipzig, Leipzig, Germany. 5 Department of