ESTRO 2023 - Abstract Book

S1546

Digital Posters

ESTRO 2023

meet the criterion which is ≤ 1.0, however, IORT (mean NTCP ≈ 0.555) is superior to VMAT (mean NTCP ≈ 0.575) for NTCP results as expected. IORT and VMAT plan comparison for GI and NTCP results was shown in Figure-2.

Conclusion Xoft Axxent eBX system is better to reduce OARs dose and it is superior to VMAT plan especially when the target has close proximity to critical structures. Moreover, low energy IORT system provides better control in low dose region at outside of the target and it results better GI which it is indicating greater dose falloff and better dose conformity. As a result, the unique dosimetry of IORT has potential to increase radiobiological advantages in achieving local control of single target brain tumors. However, detailed investigation in conjunction with radiation necrosis and novel systemic treatments after surgery is crucial.

PO-1818 Hypo-fractionated radiotherapy with SpaceOAR for prostate cancer treated with Radixact TomoTherapy

S. Can 1 , D. Karaçetin 2 , H. Tatlı 3 , Ö. Atilla 1 , N. Nalbant 1

1 Basaksehir Cam and Sakura City Hospital, Radiation Oncology, Istanbul, Turkey; 2 Basaksehir Cam and Sakura City Hospital , Radiation Oncology, Istanbul, Turkey; 3 Elekta Instrument Turkiye, İ stanbul Liaison Office, Istanbul, Turkey Purpose or Objective The aim of this study was to evaluate the effect of injecting a temporary hydrogel SpaceOAR between the rectum and the prostate and the quantify the different hypo-fractionated radiotherapy (HFRT) delivered with Radixact TomoTherapy in terms of rectal dosimetry improvement using Elekta ProKnow DS. Materials and Methods Before and after injection of hydrogel SpaceOAR, 8 patients underwent CT with 2 mm slice thickness and the T2 weighted MRI sequences were fused with CT for target delineation. Hydrogel SpaceOAR was injected to patients under general