ESTRO 2025 - Abstract Book

S1154

Clinical – Lower GI

ESTRO 2025

Results: Out of 211 initially identified studies (Figure 1), 83 and 78 were included in the descriptive and meta-analysis, respectively.

Older studies used 3D, while more recent studies used IMRT/VMAT (median publication date: 2012 vs. 2019). The boost was delivered either sequentially or simultaneously in equal proportions. RT preparation was inconsistently reported but often included a bladder filling protocol. MRI was the most commonly used imaging for GTV delineation. CTV definitions varied widely, from the tumour-only to the entire presacral and mesorectal spaces. Variability was also observed in RT boost dose and concomitant chemotherapy. The use of IMRT/VMAT (p=0.007), simultaneous boost (p=0.020), dose escalation (p=0.035), and induction and consolidation chemotherapy (p=0.023) were significantly associated with higher pCR rates in planned surgery studies (Figure 2).