S858
Clinical - Mixed sites & palliation
ESTRO 2026
treatment with 6FF; the use of flattening-filter-free energies, can further reduce times by >50%. Results: The cohort averaged 2.7 metastases per patient (range 1–16). Mean target diameter was 1.16 ± 1.4 cm (range 0.44–3.45 cm). Across all cases, WBD mean was 0.87 Gy, V12Gy 6.1 cc, V5Gy 31.8 cc, and beam-on time 10.1 min.1 metastasis (DCA n=14, VMAT n=397): VMAT reduced WBD (0.45 vs. 0.75 Gy; V12 3.4 vs. 5.5 cc; V5 12.3 vs. 18.8 cc) with slightly longer beam-on (7.8 vs. 6.6 min).2–5 metastases (DCA n=112, VMAT n=95): VMAT achieved lower WBD (0.93 vs. 1.49 Gy; V12 6.5 vs. 9.2 cc; V5 33.8 vs. 46.3 cc) and shorter beam-on (9.1 vs. 14.4 min). ≥ 6 metastases (DCA n=39, VMAT n=2; >10: DCA n=4, VMAT n=1): Although only few VMAT cases were available in this subgroup, they showed a trend toward shorter beam-on times (e.g., 16.4 vs. 20.7 min for 6–10 lesions; 19.9 vs. 33.2 min for >10).
The results of this study indicate that QoL changes after palliative RT for non-bone lesions are similar to those for bone metastases, providing a basis for future development in this underexplored area. References: 1. Koide Y, Noguchi M, Shindo Y, et al. Pain response to palliative radiotherapy in bone metastases vs. non- bone lesions: Prospective study. Radiother. Oncol. 2025;208:110901.2. Koide Y, Shindo Y, Noguchi M, et al. Quality of life report associated with pain response and patient classification system for palliative radiation therapy: A prospective observational study. Int. J. Radiat. Oncol. Biol. Phys. 2025;121:1125– 1133.3. Koide Y, Shindo Y, Nagai N, et al. Classification of patients with painful tumors to predict response to palliative radiation therapy. Int. J. Radiat. Oncol. Biol. Phys. 2024;120:79–88. Keywords: palliative radiotherapy, Quality of Life
Digital Poster 281
Whole-brain exposure and treatment efficiency in C-arm single-isocenter stereotactic radiosurgery of brain metastases Maximilian Grohmann, Andrea Baehr, Manuel Todorovic, Cordula Petersen Department of Radiotherapy and Radiation Oncology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
Purpose/Objective: Minimizing whole-brain dose (WBD) during
Fig.: Comparison of DCA and VMAT plans across metastasis clusters showing whole-brain mean dose (top), V12 Gy (middle), and beam-on time (bottom). Boxes indicate interquartile range with mean ( ◆ ) and Automated planning for C-arm SRS showed consistent advantages of VMAT in multi-metastasis cases, with lower whole-brain exposure and faster delivery. Both VMAT and DCA yielded clinically acceptable plans without complex manual optimization, supporting their complementary role depending on local median ( ― ). Conclusion: robustness considerations. Since reported WBD values include metastases, actual normal-brain exposure relevant for toxicity is even lower. Keywords: radiosurgery, brain metastases, whole- brain dose
stereotactic radiosurgery (SRS) for brain metastases is critical to reduce risks of radionecrosis and cognitive decline. Dynamic conformal arcs (DCA) provide steeper dose gradients and are considered more robust against dosimetric uncertainties, whereas volumetric modulated arc therapy (VMAT) offers superior conformity. We compared WBD and treatment efficiency of DCA and VMAT plans generated with a dedicated treatment planning system (TPS). Material/Methods: We retrospectively analyzed 664 single-isocenter SRS plans for 1791 brain metastases treated on a TrueBeam STx linac with 6 MV flattened beams (6FF). The median prescription dose was 22 Gy (range 12–25 Gy, SD 2 Gy), consistently prescribed to cover D99% of the target. DCA was predominantly used in multi- metastasis cases for its robustness, while VMAT was selectively applied where high conformity was required (clustered lesions, OAR proximity). WBD metrics (WBDmean, V12Gy, V5Gy) and beam-on time were analyzed. Reported beam-on times reflect
Digital Poster 293 Radiotherapy to Resection Cavities Following Brain
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