S1720
Physics - Dose prediction/calculation, optimisation and applications for particle therapy planning
ESTRO 2026
V30Gy<600ccm, and for bladder v50Gy<20% and V35Gy<75%. Results: All IMPT plans fulfilled V95%>99.9% for the nominal plan and V95%>98.5% for the worst-case scenario. Photon plans were planned using VMAT in accordance with the treating department’s guidelines.Figure 1 shows the extension of the CTV-E in cranial direction compared to standard volume for 1) high risk: (5.8-6.9 cm), and 2) ultra-high risk (10.6-14.7 cm).Bladder doses were lower with proton therapy, except for one ultra-high patient. For bowel, equal or lower doses were maintained compared with the photon plans – see Figure 2. For the ultra-high patients mean kidney doses could be reduced by 3.2-15.4 Gy with IMPT.Doses to the sacrum, spinal cord, cauda equina, and femoral heads were all similar or lower with IMPT.
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Intensity modulated proton therapy (IMPT) for high- and ultra-high-target anal cancer patients according to the NOAC guidelines. Heidi S. Rønde 1 , Jesper F. Kallehauge 1 , Karen-Lise G. Spindler 2,3 , Eva Serup-Hansen 4 , Birgitte Havelund 5 , Lars Fokdal 5 , Camilla J.S. Kronborg 1 1 Danish Centre for Particle Therapy, Aarhus University Hospital, Aarhus, Denmark. 2 Department of Oncology, Aarhus University Hospital, Aarhus, Denmark. 3 Department of Clinical Medicine, Aarhus University Hospital, Aarhus, Denmark. 4 Department of Oncology, Copenhagen University Hospital, Herlev and Gentofte, Copenhagen, Denmark. 5 Department of Oncology, University Hospital of Southern Denmark, Lillebaelt Hospital, Vejle, Denmark Purpose/Objective: The Nordic anal cancer group (NOAC) suggests risk adapted delineation for anal cancer [1]. The guideline comprises instructions for Elective Clinical Target Volume (CTV-E) delineation in case of prophylactic inclusion of common iliac vessels (“high”) risk patients, but also para-aortic lymph node spread (“ultra- high”).This must be weighed against increased side effect risk [2,3]. For planning a risk adapted approach versus acceptable side effects we compared standard photon therapy versus risk adapted proton therapy for 1) High-group: standard photon vs. high proton and 2) Ultra-high group: ultra-high photon vs. ultra-high proton. Material/Methods: Five patients treated with standard photon therapy in the high-group were replanned with IMPT to the “high” CTV-E according to the NOAC guidelines. Further, three patients with paraaortic spread treated with “ultra- high” IMPT after comparative dose planning were included.Targets were prescribed as: CTV-E to 48 Gy, CTV-N to 54 Gy or 60 Gy, and CTV-T to 60 Gy.Proton plans used robust (5 mm; 3.5%) IMPT planning with three posterior fields and three anterior with a 3 cm or 5 cm range shifter, respectively.According to the Danish Anal Cancer Group (DACG) dose guidance, the objective for bowel is V45Gy<300ccm and
Conclusion: Even with the extended target volume “high” proton plans spared or maintained dose to relevant organs compared to the standard photon plans. For the “ultra-high” targets clinically, significant sparing was
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