ESTRO 2024 - Abstract Book

S470

Clinical - Breast

ESTRO 2024

generated contours would still achieve adequate CTV coverage (goal: D98%>95%) of the clinically approved contours. Additionaly, the influencer structure’s impact on target contour propagation accuracy was assessed. The online workflow was repeated using the Ethos test environment without the use of an influencer structure. The target contour propagation both with and without the use of an influencer was evaluated by a radiation oncologist assessing the need for contour adaptation.

Results:

From June 2022 to September 2023, 21 patients (n=20 WBI, n=1 PMRT) were included in the BREAST-ART trial, and treated with 5x5.2Gy. Table 1 shows dosimetric data on scheduled and adapted TP. The Wilcoxon signed rank test revealed a significant difference between scheduled TP and adapted TP for the clinical target goals. Figure 1 shows the dosimetric impact of manual corrections in the first 10 patients. The TPs evaluated on either manually corrected or automatically generated contours all met the clinical goals for all fractions. The majority of the corrections were performed in the 2 most cranial or caudal slices and had no clinically relevant impact. Targets propagated without the influencer structure were evaluated in 20 fractions of 4 patients, and resulted in less or equal manual corrections compared to targets propagated with influencer. Therefore, the use of the influencer was discontinued after 18 patients, and less corrections of targets were needed. Influencer/target structures were corrected in 52/90 and 0/15 fractions for patients treated with (n=18) and without (n=3) the influencer structure, respectively. Median treatment times were 14.2 min (+influencer; range: 10.7 – 24.6) and 11.6 min (-influencer; range: 10.9-14.3), measured from the CBCT at the start until the CBCT at the end. Patients were generally satisfied with the procedure and 20/21 patients preferred the same treatment again. Acute toxicity was mainly grade 0- 1. No toxcity grade ≥3 was observed.