ESTRO 2022 - Abstract Book

S1598

Abstract book

ESTRO 2022

Conclusion A previously developed atlas was shown to be an adequate common reference space for spatial normalisation for many organs of interest simultaneously, but performance must be improved for abdominal organs. Other label fusion approaches and more refined registration workflows should be investigated to increase mapping accuracy in small and/or highly deformable organs.

Poster (digital): Brachytherapy: Breast Poster (digital): Brachytherapy: Gynaecology

PO-1791 Lumbosacral plexus dose with CT pelvimetry correlation in cervical cancer HDR brachytherapy Withdrawn

PO-1792 Implementation of IGABT evidence-based planning aims, whilst changing brachytherapy systems

E. Flower 1 , G. Busuttil 1 , S. Zanjani 1 , D. Thwaites 2 , N. Thiru 1 , J. Chard 1

1 Crown Princess Mary Cancer Centre, Radiation Oncology, Westmead, Australia; 2 University of Sydney, Institute of Medical Physics, Camperdown, Australia Purpose or Objective To undertake a dosimetric plan quality review for locally advanced cervical cancer high dose rate brachytherapy treated using modern evidence-based planning aims from data published since the advent of MRI guided brachytherapy for cervix cancer. Materials and Methods Patients were treated with curative intent chemoradiotherapy followed by a brachytherapy boost. Planning aims were based on the EMBRACE II trial protocol [1] and more recent publications [2]. The brachytherapy boost was delivered in three fractions. Interstitial needles were available when clinically indicated. All patients were planned using MR guidance, with both volume and graphical optimization tools available. Since this institution implemented modern evidence-based planning aims, a change in brachytherapy systems was also undertaken, including change in applicator design. The applicator in the first system was the Fletcher-Suite-Delclos applicator, with or without interstitial components. In the second system, the Advanced Gynaecology Applicator (Venezia) was available, together with parallel and oblique needles and vaginal caps. Dose volume histogram parameters, point doses, TRAK, from treatment plans were retrospectively collected. Changes in plan quality measures over time are reported. All doses are reported as EQD2, combined with EBRT.

Results 61 patients were treated since the implementation of modern evidence-based planning aims. The mean CTV-HR dose for the first system was 92Gy, and 90.9Gy for the second system. The average bladder D2cc decreased from 78.6Gy to 73.9Gy, average rectum D2cc decreased from 61.0Gy to 59.8Gy and average sigmoid decreased from 60.3Gy to 57.2Gy. 80.3% of