ESTRO 2025 - Abstract Book

S4044

RTT - Patient care, preparation, immobilisation and IGRT verification protocols

ESTRO 2025

Material/Methods: We retrospectively evaluated 24 patients who underwent re-RT combined with HT between 2022 and 2023. Twelve patients were positioned using a vacuum mattress, while the remaining twelve with soft cushions. Vacuum mattresses were borrowed from radiotherapy and the patient was treated in a vacuum mattress based on availability. For both groups, the applied power, the maximum, minimum, and mean reached temperatures were recorded. These data were used to calculate inter-fraction temperature differences. A t-test was conducted to compare the inter-fraction temperature differences between the two groups. We also analyzed toxicity differences between the two groups. Since applied power can influence the measured temperatures, the data were adjusted to account for its effect. This was done by calculating the intraclass correlation coefficient (ICC) followed by a bootstrapping technique to generate a reliable ICC confidence interval by simulating 24 patient substitutes 10000 times. The ICC was calculated for each group to assess the consistency of temperature measurements. The ICC values were compared using a two-sample t-test. Results: The maximum, minimum, and mean inter-fraction temperature differences are presented in Table 1. The vacuum mattresses group exhibited significantly lower inter-fraction temperature differences (p < 0.05) compared to the soft cushions group. After adjusting for applied power, the ICC was 0.32 for the soft cushion group and 0.81 for the vacuum mattress group, with a significant difference (p ≤ 0.001). No differences in toxicity were observed during or after treatment.

Conclusion: Our findings suggest that using a vacuum mattress for patient positioning during HT, results in more stable and reproducible positioning, leading to lower inter-fraction temperature differences without increasing toxicity. These