ESTRO 2025 - Abstract Book

S1235

Clinical – Lower GI

ESTRO 2025

3381

Digital Poster hypofractionated proton therapy for primary intrahepatic cancers: time for a pivotal role? a systematic review and meta-analysis Marianna Alessandra Gerardi 1 , Luca Bergamaschi 1 , Maria Giulia Vincini 1 , Stefania Volpe 1,2 , Sara Gandini 3 , Aurora Gaeta 3 , Annamaria Ferrari 1 , Gaia Piperno 1 , Valentina Stellari 1,2 , Chiara Lorubbio 1,2 , Nicola Fazio 4 , Uberto Fumagalli Romario 5 , Franco Orsi 6 , Maria Giulia Zampino 4 , Roberto Orecchia 7 , Barbara Alicja Jereczek-Fossa 1,2 , Daniela Alterio 1 1 Division of Radiation Oncology, European Institute of Oncology IRCCS, Milan, Italy. 2 Department of Oncology and Hemato-oncology, University of Milan, Milan, Italy. 3 Department of Experimental Oncology, European Institute of Oncology IRCCS, Milan, Italy. 4 Division of Gastrointestinal Medical Oncology and Neuroendocrine Tumors, European Institute of Oncology IRCCS, Milan, Italy. 5 Digestive Surgery, European Institute of Oncology IRCCS, Milan, Italy. 6 Department of Interventional Radiology, European Institute of Oncology IRCCS, Milan, Italy. 7 Scientific Directorate, European Institute of Oncology IRCCS, Milan, Italy Purpose/Objective: Hypofractionated proton therapy (PT) is gaining an increasing crucial role in the curative treatment of primary intrahepatic cancers (PIC), especially for hepatocellular carcinoma (HCC). However, significant inhomogeneities in terms of indication, fractionation schedules, efficacy and safety of this strategy is reported. The present work aims to provide a systematic critical review of the available literature on hypofractionated PT in the field of PIC and to investigate potential factors predictive for local control. Material/Methods: This systematic review and meta-analysis complied with the PRISMA recommendations. Inclusion criteria were curative-intent hypofractionated (≥3 Gy (RBE)/fraction) PT for PIC and availabilities of clinical outcomes reported in the study. The bibliographic search was performed on the NCBI Pubmed, Embase, Scopus and Web of Science in November 2023. For each included study, the Biological Effective Dose (BED) was calculated (α/β = 10 Gy for PIC) and a BED cut-off of 100 Gy was used as a threshold for stratifying selected clinical outcomes within two subgroups (BED <100 Gy and > 100 Gy, respectively). Results: Among a total of 1.988 documents, 15 studies ( Table 1 ) met the inclusion criteria for the quantitative analysis and were considered for the purpose of the current work. The total number of patients included was 1.131. The median follow-up across the studies (data available for 14/15 studies) was 30 months. Considering the median maximum tumor diameter reported in the studies (data available for 14/15 studies), the median tumour size across all studies was 4.75 cm (range 2.6 – 6.0 cm). The median proportion of patients classified as Child A was 73.1%. The median BED value across the studies was 93.58 Gy (RBE). The local summary control (LC) rate was 92% (95% CI 90%-94%). The showed no significant heterogeneity between studies ( Figure 1 ). A statistically significant association was found between the tumour size and the LC, both considering tumor size as a continuous variable (p = .014) and using the median value of 4.75 cm as cut-off (p = .003). Moreover, a borderline association between a BED ≥ 100 Gy (RBE) and a higher LC was found (p=0.06).