ESTRO 2022 - Abstract Book

S498

Abstract book

ESTRO 2022

dropped to 72.8% at 10 years (p <0.001), with hormonal blockade 90.9% and without hormones 66.8%, and it was worse if they had exclusive BT. The BRFS at 10 years in T1c was 95%, compared to 84% in T2 (p <0.001). The initial PSA> or <10 showed no differences. With involvement of> 50% of the cylinders, it fell to 80% at 10 years (p <0.001). In 154 patients up to 60 years of age, the BRFS at 10 years was 97.6%. There were complications in 18'3% with exclusive BT and 33.3% in combined. Urological toxicity was 18.7% (16.9% in exclusive BT vs 26.1% in EBRT + BT), ≥ G2 in 13.3% and ≥ G3 in 5.8%. Rectal toxicity was very low, 4% (2.5% in BT alone and 10.1% in RT + BT), ≥ G2 in 1.6% and ≥ G3 in 0.1%.

Conclusion BT with I-125 seeds is a very effective long-term treatment in low and intermediate risk prostate carcinoma. In cases with Gleason 4 + 3 or> 50% affected cylinders, there are more relapses, and we recommend triple treatment with EBRT + BT + hormonal blockade for 6 months. Toxicity is limited in cases with combined treatment and very low with exclusive BT. BT with I-125 seeds should be offered to selected patients as the first therapeutic option, especially in young patients.

PD-0569 Assessment of Catheter Displacement on Single Fraction HDR Prostate Brachytherapy Treatment

S.K. Abdul Wahab 1 , M. Boutros 2 , G. Sands 2 , A. Nisbet 1

1 University College London, Department of Medical Physics and Biomedical Engineering, London, United Kingdom; 2 University College London Hospital, Radiotherapy Department, London, United Kingdom Purpose or Objective In CT-planned HDR prostate brachytherapy the time delay of ~2 to 3 hours between the insertion of catheters and treatment delivery may bring about inaccuracies to the treatment delivery due to catheter displacement. The catheter position in the scanned image, used to plan a treatment, may not match the true positions in the patient during treatment. In such cases, the catheters may need to be repositioned and the procedure repeated. This prolongs the treatment procedure and may lower the quality of the treatment. This study involves evaluating the impact of the catheter displacement in single fraction HDR prostate brachytherapy treatment. Materials and Methods 20 patients had simulated catheter displacement introduced on Oncentra Brachy. The catheter shifts were simulated in two ways, synchronous and selective catheter shift. For the former, for each treatment plan, all catheters were displaced uniformly through known values. For the latter, catheters were selectively displaced, based on the segment of the planning target volume (PTV) where they were positioned; anterior, middle and posterior segment as shown in Figure 1. The dose coverage to the PTV, urethra, bladder and rectum were then evaluated using the parameters of dose coverage to 90% of the PTV volume, D90, dose accumulated by 30% of the urethra volume, D30, and the volume of the bladder and rectum receiving 70% (10.5 ) of prescribed dose, V70.