S323
Clinical - Breast
ESTRO 2026
References: Holt F, Probert J, Darby SC, et al.Proton Beam Therapy for Early Breast Cancer: A Systematic Review and Meta-analysis of Clinical Outcomes.Int J Radiat Oncol Biol Phys. 2023;117(4):869-882.DOI: https://doi.org/10.1016/j.ijrobp.2023.02.023Kammerer E, Le Guevelou J, et al.Proton therapy for locally advanced breast cancer: A systematic review of the literature.Cancer Treat Rev. 2017;61:45- 56.DOI: https://doi.org/10.1016/j.ctrv.2017.11.006 Keywords: Prone, Proton-PBS, Gantry-less Digital Poster Highlight 4312 Stereotactic radiotherapy and novel drugs for brain metastases from breast cancer: RABBIT-NEW TRIAL, an observational multicentric retrospective study Lucia Pia Ciccone 1 , Camilla Delli Paoli 1 , Fiammetta Meacci 1 , Saverio Caini 2 , Carlotta Giandini 3 , Barbara D'Andrea 4 , Valentina Borzillo 5 , Lodoviga Giudice 6 , Lucrezia Toppi 7 , Silvia Mariani 8 , Elena Clerici 9 , Francesca Giugliano 10 , Tiziana Talienti 11 , Damiano Balestrini 12 , Francesca Rossi 13 , Maria Carmen De Santis 3 , Alba Fiorentino 11 , Grazia Lazzari 4 , Rossella Di Franco 5 , Karol Migliorati 14 , Paolo Matteucci 7 , Silvia Chiesa 8 , Pierina Navarria 9 , Cesare Guida 10 , Silvia Scoccianti 1 1 Radiation Oncology Unit, Ospedale Santa Maria Annunziata, Azienda USL Toscana Centro, Firenze, Italy. 2 S.C. Epidemiologia dei Fattori di Rischio e degli Stili di Vita, Istituto per lo studio, la prevenzione e la rete oncologica (ISPRO), Firenze, Italy. 3 S.C Radioterapia Oncologica, S.S Radioterapia dei Tumori della Mammella, Fondazione IRCCS "Istituto Nazionale dei Tumori", Milano, Italy. 4 Radioterapia, IRCCS CROB, Rionero In Vulture, Italy. 5 Radioterapia Oncologica, Istituto Nazionale Tumori - IRCCS - Fondazione G. Pascale, Napoli, Italy. 6 Radioterapia, Poliambulanza Istituto Ospedaliero, Brescia, Italy. 7 Radioterapia, Fondazione Policlinico Universitario Campus Bio- Medico, Roma, Italy. 8 Gemelli advanced Radiotherapy, Fondazione Policlinico Universitario Gemelli IRCCS, Roma, Italy. 9 Dipartimento di Radioterapia e Radiochirurgia, IRCCS Humanitas Research Hospital, Rozzano, Italy. 10 Radioterapia, Asl Na 1 Ospedale del Mare, Napoli, Italy. 11 Department of Medicine, LUM University, General Regional Hospital "F. Miulli", Acquaviva delle Fonti, Italy. 12 Radiotherapy Department, Bellaria Hospital, AUSL Bologna, Bologna, Italy. 13 Radiation Oncology Unit, Ospedale Misericordia, Azienda USL Toscana Sud Est, Grosseto, Italy. 14 Radioterapia, Fondazione Poliambulanza Istituto Ospedaliero, Brescia, Italy
Material/Methods: We chose five patient cases that were treated in prone position in our clinic using the Orfit Industries NV (Wijnegem, Belgium) prone couch overlay. We have re- planned them on the P-Cure system with table top using RaySearch inc. (Stockholm, SW) TPS that is commissioned for P-Cure system.The prescription dose in these cases was 26 Gy to the breast and 30 Gy simultaneous integrated boost to the tumor bed in 5 fractions. We used 9 field pseudo 90 degrees arc plan starting with a superior- inferior beam and concluding with a lateral beam. The Proton plans were compared to supine plans that were delivered on the True Beam (Varian inc. Palo Alto USA). Results: Proton plans showed about 0.1 Gy mean Lung dose and about 0.02 Gy mean heart dose. The photon ones showed about 0.3Gy and 0.15 Gy mean lung and heart doses respectivly. The major advantage was a conformal tumor bed dosage with small additional dose to the non-boost-PTV. To quantify this, we compared to the C-arm Linac the volume of the PTV receiving about 103% that varied between 12% to 22%. For the P-Cure delivery it was found between 3.5% to 4.0%.
Conclusion: We have showed feasibility to deliver Prone pseudo arc PBS treatments using the P-Cure system, with orthogonal setup X-rays at perpendicular couch position. This delivery allows treating the breast itself with out the risk of overshooting to the lungs at the distal edge. We showed conformal SIB with minimum hot spot to the PTV. Future study will investigate whether low 50 MeV Synchrotron energy will revoke the range shifter necessity for these beams.
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