ESTRO 2025 - Abstract Book

S2361

Interdisciplinary – Other

ESTRO 2025

dose, and target coverage were secondary endpoints. Prior to CT-acquisition, included patients tested the matt and mattress at the CT-scanner couch by lying on each in RT-position for one minute. During testing, patient preference and experienced pain (Numerical Rating Scale, NRS, 0-10) 1 were scored. Subsequently, patients were scanned and treated on their preferred matt or mattress. As it turned out most included patients preferred the RT-Comfort mattress, positioning stability on the standard matt was evaluated in a historical cohort. During the first five minutes of treatment, positioning stability was measured using optical surface scanning and evaluated using linear regression. The effect of the RT-Comfort mattress on maximum skin dose and V95% PTV coverage were evaluated by accounting for the mattress in clinical treatment plan recalculation and re-optimization. Results In total, 44 out of 45 included patients (98%) preferred the RT-Comfort mattress, with strong preference in 35 patients (p<0.0001). The median pain score (Figure 1) was reduced (p<0.0001) from 4.8 (IQR: 2.0-6.1) NRS on the standard matt to 2.0 (IQR: 0.4-4.0) NRS on the RT-Comfort mattress, which is considered clinically significant 1 . For both negligible sinking-in was observed (Figure 2), although marginally smaller (p<0.0001) for the RT-Comfort mattress (0.05 mm/min) compared to the standard matt (0.12 mm/min). The RT-Comfort mattress increased the calculated maximum skin dose from 82.7% (SD: 16.3%) to 88.5% (SD: 16.4%), which could be fully recovered to 80.8% (SD 16.7%) by accounting for the RT-Comfort mattress during plan optimization. No relevant effect on target dose was observed.