ESTRO 2021 Abstract Book

S1019

ESTRO 2021

Unit, Gemelli Molise Hospital – Università Cattolica del Sacro Cuore, Campobasso, Italy; 7 Medical Physics, IRCCS Azienda Ospedaliero-Universitaria di Bologna, Bologna, Italy

Purpose or Objective To perform an updated systematic review on concurrent chemoradiation (CRT) in unresectable, non- metastatic biliary tract cancers (BTC). Materials and Methods A literature search based on Pubmed, Scopus, and Cochrane Library was performed. Only English-written papers published over the last 12 years (from 2008 to 2020 included) were screened. Only papers reporting outcomes after concurrent CRT in unresectable BTC were selected. Results A total of 1766 patients with primary or locally recurrent unresectable BTC were included in the analysis. Median radiotherapy (RT) dose ranged from 45.0 to 72.6 Gy, with conventional fractionation. Chemotherapy (CHT) protocols were variable. Median follow-up (FU) ranged from 9.0 to 27.6 months. From the analysis of selected studies median progression-free survival and overall survival were 13.5 and 8.1 months, respectively. Grade ≥ 3 acute haematological toxicity was recorded in five studies and ranged from 8.1 to 50.0 % (median 21.7 %). Also, grade ≥ 3 gastrointestinal toxicity was registered in 5 studies and ranged from 0.0 to 22.0 % (median 10.6 %). Clinical outcomes are summarized in Table 1. Conclusion Concurrent CRT was a safe and effective option in unresectable BTC. CRT showed a significant benefit compared to CT alone in several trials included in our analysis. Limited data are available about the impact of modern techniques. Moreover, prospective randomized trials directly comparing systemic treatments and CRT are lacking.

PO-1235 Feasibility and early clinical experience of online adaptive MR-guided radiotherapy of liver tumors P. Rogowski 1 , R. von Bestenbostel 1 , F. Walter 1 , K. Straub 1 , L. Nierer 1 , G. Landry 1 , M. Reiner 1 , C. Kurz 1 , C.J. Auernhammer 2 , C. Belka 1 , M. Niyazi 1 , S. Corradini 1 1 University Hospital, LMU Munich, Department of Radiation Oncology, Munich, Germany; 2 University Hospital, LMU Munich, Department of Internal Medicine 4, Munich, Germany Purpose or Objective Stereotactic body radiotherapy (SBRT) has gained importance in the treatment of primary and secondary liver tumors due to promising local control rates. However, adjacent organs at risk (OAR) frequently limit the applicable dose to the target volume. The introduction of hybrid magnetic resonance imaging (MRI)-guided radiotherapy systems (MR-linac) may in future allow dose escalation strategies with better OAR sparing due to improved soft tissue visualization, adaptive treatment planning and real-time motion management. However, current clinical experience with this relatively new technique is sparse. This study reports our initial institutional experience and analyses the feasibility and early results of online adaptive MR-guided radiotherapy (oMRgRT) of liver tumors. Materials and Methods We retrospectively examined consecutive patients with primary or secondary liver lesions treated at our institution using a 0.35T hybrid MR-Linac (Viewray Inc., Mountain View, CA). Contrast agent was given in 38% of patients. Online-adaptive treatment planning was used to account for interfractional anatomical changes, and real-time intrafractional motion management using online 2D cine MRI was performed using a respiratory