ESTRO 2022 - Abstract Book

S1130

Abstract book

ESTRO 2022

one fig.1. Acute genitourinary (GU) and gastroenteric (GI) toxicity was ≤ G2 and all patients completed treatment in 8 weeks. Late GU toxicity ≥ G3 was reported in patients who received BRT boost (in 2 patients G3 and in 1 patient G4, requiring temporary colostomy). No patients presented > G2 late GI toxicity. Fig.1 Overall survival is lost at follow-up. Overall survival is shown in

Conclusion At state of art, brachytherapy is mandatory within cervical cancer radiation strategies. A dose escalation with EBRT could provide to a tumor downsizing useful when only endocavitary without combined interstitial brachytherapy is available but insufficient to cover high volume residual primary. Unfortunately, in our series, hypofractionated EBRT plus BRT it's more toxic than standard treatment. Moreover, in elderly patients or in patients with technical impossibility to receive BRT, external dose escalation could represent an alternative and this schedule seems to be useful in local control. More trials including higher number of patients are necessary to define the real role of hypofractionation in cervical cancer.

PO-1334 Atlas Based Autosegmentation Of Organs At Risk In Gynaecological Cancer

P. Caricato 1,2 , S. Trivellato 1 , E. Bonetto 1 , V. Faccenda 1,2 , D. Panizza 1,3 , S. Arcangeli 4,3 , S. Meregalli 4

1 ASST Monza, Medical Physics Department, Monza, Italy; 2 University of Milan, Department of Physics, Milan, Italy; 3 University of Milan Bicocca, School of Medicine and Surgery, Milan, Italy; 4 ASST Monza, Department of Radiation Oncology, Monza, Italy Purpose or Objective Accurate segmentation of organs at risk (OARs) and target volumes is crucial for radiation treatment planning but highly time-consuming. One commercially available solution is atlas-based auto-segmentation (ABAS, Elekta, Stockholm). Its use aims to reduce time-consumption and inter- and intra-observer’s variability, which may significantly affect dosimetric parameters. The purpose of this study was to investigate the use of ABAS in gynecological clinical routine. Materials and Methods This feasibility study retrospectively selected 23 patients treated with external beam radiation therapy (EBRT) between 2019 and 2021. Ten out of 23 structure sets were used to create an atlas library in ABAS containing bladder, rectum, and femoral heads carefully defined by two skilled radiation oncologists. The remaining 13 patient CTs were used to test the library performances. The following contour comparison was performed using the Hausdorff distance (HD), the Mean Distance to Agreement (MDA), the Dice similarity Index (DI), and the Jaccard Index (JI). The results were compared performing the Wilcoxon Mann Whitney test to assess statistical significance ( α =0.05). Results The auto-segmentation process required about 6 minutes for each CT set. Figures 1 and 2 show the geometrical metric results. The median HD, MDA, DI, and JI values for the right femoral head were 7.44 mm [3.66 – 17.77 mm], 1.20 mm [0.67 – 2.12 mm], 0.89 [0.80 – 0.93], and 0.80 [0.67 – 0.88], retrospectively; for the left femoral head were 7.53 mm [3.87 – 15.54 mm], 1.13 mm [0.74 – 1.39 mm], 0.91 [0.86 – 0.93], and 0.84 [0.76 – 0.87]. On the other hand, median metric values for the bladder were 20.64 mm [12.00 – 34.95 mm], 3.13 mm [1.93 – 11.21 mm], 0.80 [0.36 – 0.87], and 0.66 [0.22 – 0.77], respectively. Lastly, the median metric results for the rectum were 23.79 mm [14.81 – 42.56 mm], 3.58 mm [2.19 – 9.98 mm], 0.64 [0.34 – 0.81], and 0.47 [0.21 – 0.68], respectively. The data comparison showed comparable ABAS performances in rectum and bladder segmentation (p > 0.05) and in right and left femoral heads (p > 0.05). A significant difference was registered for ABAS segmentation performances in bilateral-femoral heads compared to rectum and bladder (p << 0.05).