ESTRO 2025 - Abstract Book

S1174

Clinical – Lower GI

ESTRO 2025

Results: In total, 42 of 63 (67%) of UK radiotherapy centres answered the repeat IMRT rectal survey; including 70 MDTs answering the clinical scenarios questions. There was improvement in many delivery aspects recommended by the guidance for example: the routine use for all patients of IMRT/VMAT (95%, previously 68%), treatment over 25 fractions (98%, previously 77%), use of a simultaneous integrated boost (SIB) in all patients (46%, previously 16%), peer review in all patients (66%, previously 39%), IV contrast (98%, previously 81%), rectal filling protocol (85%, previously 58%), using standard constraints (93%, previously 0%) and delineation of small bowel loops (59%, previously 39%). There has been an improvement in all of these aspects of treatment in comparison to the 2020 audit. While the intention of the guidance was to suggest SIB in all long course patients, SIB in selected patients was used in 56% of centres despite 93% of centres confirming they were using the guidance as routine. There was wide variation in neo-adjuvant treatment approaches used between MDTs in the clinical questions, with consensus on the most desirable treatment strategy ranging from only 24% to a maximum of 57% across the five clinical scenarios. Figure 2 illustrates variation detailing answers to 2 questions.