Statistical analysis
The Wilcoxon signed-rank test was used to compare rectum doses based on MR1 to rectum doses based on MR0, MR2 and MR3. The differences in volume and shape/thickness of the ROIs were also tested with Wilcoxon. The tests were two-sided and considered significant if All statistical analyses were performed using the software SPSS statistics 27 (IBM, Armonk, New York, United States).