S691
Clinical – Lower GI
ESTRO 2026
neoplasms," and "dosimetry." Included studies reported comparative dosimetric data (PT vs. photon techniques) or clinical outcomes for GC. Two reviewers independently screened records, extracted data, and assessed quality. Results: From 487 identified records, 15 studies met inclusion criteria. Synthesized evidence consistently demonstrates PT's superiority in OAR sparing. Pooled analysis shows PT significantly reduces mean dose to kidneys (mean difference: -5.8 to -7.2 Gy), liver (-4.5 to -6.1 Gy), and heart (V25Gy reduction >60%) compared to VMAT/IMRT, while maintaining optimal target coverage. Early clinical data suggest a correlative trend towards reduced toxicities. Conclusion: This systematic review provides robust evidence that proton therapy serves as an effective physical targeted modality in gastric cancer. By significantly reducing radiation dose to critical OARs, PT holds strong potential to mitigate toxicity barriers limiting combined-modality regimens. These findings support prospective trials validating PT as a foundational platform for next-generation targeted strategies in GC. References: 1. Wang et al. Int J Radiat Oncol Biol Phys. 2021;109(1):235-243.2. Hong et al. Radiother Oncol 2019;133:71-78. Keywords: Proton Therapy, Gastric Cancer, Treatment Planning Neoadjuvant RTQT Combined with Locoregional Hyperthermia in LARC: Feasibility and Tolerance of Short-Course Versus Long-Course Radiotherapy Schedules Laura Ferrera Alayón 1 , Bárbara Salas Salas 1 , Antonio Alayón-Afonso 1 , Miguel Sánchez Carrascal 2 , Laura López-Molina 1 , Rafael Alexis Hernández-Santana 1 , Alba López-Carmona 1 , Gemma Calvet-molinas 3 , Nereida Rodriguez-González 1 , Hans Crezee 4 , Marta LLoret Sáez-Bravo 1 1 Radiation Oncology, Universitary Hospital Dr Negrin, Las Palmas de Gran Canaria, Spain. 2 Medical Physics,, Universitary Hospital Dr Negrin, Las Palmas de Gran Canaria, Spain. 3 Radiation Oncology, University Hospital Santa Creu i Sant Pau, Barcelona, Spain. 4 Radiation Oncology, University of Amsterdam, Cancer Center Amsterdam, Amsterdam, Netherlands Purpose/Objective: Integrating deep regional hyperthermia (HT) with neoadjuvant chemoradiotherapy (CRT) may enhance treatment efficacy in locally advanced rectal cancer (LARC). However, feasibility and tolerance data remain Digital Poster Highlight 1047
analyses did not alter these results. No publication bias was detected.Qualitative synthesis indicated that sarcopenia was linked to severe hematologic side effects and to chemotherapy modifications in two studies, while no study demonstrated an effect on radiotherapy delivery. Conclusion: Sarcopenia affects approximately one-third of ASCC patients and is associated with a nearly threefold increased risk of death, without a significant impact on DFS, which suggests that it may reflect impaired physiological reserve rather than increased recurrence risk. Sarcopenia is linked to hematologic adverse events and chemotherapy modifications, but not to radiotherapy interruptions. Prospective studies with standardized definitions and functional assessments are needed to clarify its prognostic role in patients with ASCC treated with chemoradiotherapy. References: 1. Shachar SS et al. Eur J Cancer 2016;57:58.2. Ramírez-Giraldo C et al. J Gastrointest Cancer 2025;56:171.3. Bingmer K et al. J Surg Oncol 2020;121:1148.4. Nilsson MP et al. Radiat Oncol 2021;16:152.5. Martin D et al. Front Oncol 2020;10:1576.6. Mohamed AA et al. Cancers (Basel) 2022;14:4521.7. Gadam RK et al. Int J Radiat Oncol Biol Phys 2023;117(2S):e297. Keywords: Anal canal cancer, Sarcopenia; Overall survival Proton therapy in gastric cancer: a systematic review of dosimetric and clinical evidence Meysam Ghanbari Saray 1 , Mushvig Hasanov 2 , Aykhan Abbasov 2 , Minhaalu Hassan Ali 1 , Matin Ghods 1 1 Scientific Research Center, Azerbaijan Medical University, Baku, Azerbaijan. 2 Department of General surgery, Azerbaijan Medical University, Baku, Azerbaijan Purpose/Objective: Molecular targeted therapies have expanded gastric cancer (GC) treatment options, but their synergy with radiotherapy is limited by toxicity concerns from incidental irradiation of organs-at-risk (OARs). Proton therapy (PT) offers a potential solution through its physical targeting capability (Bragg Peak). This systematic review synthesizes existing dosimetric and clinical evidence on PT for GC, evaluating its potential to enhance the therapeutic ratio. Material/Methods: A systematic literature search was conducted following PRISMA guidelines. Databases (PubMed, Scopus, Web of Science) were queried (2000-2024) using keywords: "proton therapy," "gastric cancer," "stomach Digital Poster 968
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