ESTRO 2022 - Abstract Book

S352

Abstract book

ESTRO 2022

Conclusion We obtained a similar spectrum of bacteria from the initial and middle urine streams. We also showed that there is a change in bacteria species is affected by the treatment of prostate cancer patients. NCN 2020/39/B/NZ7/02733

PD-0408 Long-term outcome after definitive photon vs. combined proton/photon irradiation for prostate cancer

S.A. Koerber 1 , K. Ebel 1 , R. Lotsch 1 , J. Ristau 1 , C.A. Fink 1 , F. Schunn 1 , I. Schlampp 1 , J. Rademacher 1 , T. Holland-Letz 2 , S.B. Harrabi 1 , J. Debus 1 , K. Herfarth 1 1 Heidelberg University Hospital, Department of Radiation Oncology, Heidelberg, Germany; 2 German Cancer Research Center, Department of Biostatistics, Heidelberg, Germany Purpose or Objective Due to their physical characteristics, protons have a great potential to treat patients with prostate cancer. While reduced toxicity, improved outcome and cost-effectiveness have been discussed, there is a lack of robust clinical data so far. Thus, the debate in treating early prostate cancer with proton beam therapy is still active. Therefore, the current study aimed to analyze long-term outcome of a large cohort of prostate cancer patients treated with either photons or photons and protons. Materials and Methods For this retrospective study, we included 549 men with stage T1-T3 N0 M0 treatment-naïve prostate cancer irradiated at our department in the period from 2010 to 2019. Patients received either conventional photon-based intensity-modulated radiotherapy with daily image guidance (IMRT/IGRT) (CT cohort) or combined photon radiotherapy with a proton boost using active raster scanning technique (PT cohort). Acute and late adverse events were evaluated according to CTCAE criteria and quality of life according to QLQ-C30 and -PR25 questionnaire. Further endpoints were overall survival (OS) and biochemical progression-free survival (bPFS). For statistical analyses we used the log-rank and chi-squared test. Results The CT cohort consisted of 398 men while 151 patients were included in the PT group. Both cohorts were well-balanced, most patients were classified as intermediate-risk according to d’Amico risk classification (68.3% for CT vs. 70.2% for PT). Median follow-up was 58.9 months for the photon group and 49.0 months for the group with a proton boost. There were no statistically significant differences regarding clinical outcome with a 5- and 10-year overall survival of 92.5% vs. 93.7% and 69.6% vs. 77.5% (CT vs. PT). 5- and 10-year biochemical progression-free survival (bPFS) were 90.0% and 57.1% for the photon group and 84.9% and 50.2% for the proton boost cohort, respectively. During treatment, there was a higher risk for gastrointestinal (GI) toxicity for some items (e.g. grade 2 rectal urgency: 6.1% vs. 0.7%), however, these differences disappeared during long-term follow-up. The global quality of life at the time of the last follow-up demonstrated no statistically significant difference between both groups with a mean score of 70.7 (SD 21.2) for the CT and 70.6 (SD 21.9) for the PT cohort. Conclusion Our findings obtained from a large cohort confirmed the long-term efficacy of definitive irradiation of patients with treatment-naïve prostate cancer using a proton boost. However, these results also suggest that there was no considerable decrease of toxicity when compared to conventional photon irradiation. Thus, data from prospective randomized trials like the phase III randomized clinical trial of proton therapy versus IMRT for low or intermediate risk prostate cancer (NCT01617161) are highly expected. 1 Shahid Beheshti University of Medical Science, Radiotherapy Oncology, Tehran, Iran Islamic Republic of; 2 Iran University of Medical Sceince, Medical Physics, Tehran, Iran Islamic Republic of Purpose or Objective Accurate delineation of prostate and organs at risk (OARs) in CT images plays an important role in both external beam radiotherapy (EBRT) and brachytherapy treatment planning but due to the low soft contrast tissue, it is a very time- consuming and challenging task and prone to inter and intra-observer variations. In this work, we propose a two-stage deep learning-based approach for fast, reliable, and reproducible auto-segmentation of prostate and OARs in EBRT and brachytherapy. Materials and Methods In our segmentation framework, the first stage is the organ localizer module, which generates a candidate segmentation region of interest (ROIs) for each organ. The second stage produces a more robust and accurate contour from the previous coarse segmentation mask. A 3D-Unet with attention mechanism on skip connections and deep supervision concept will generate ROIs by eliminating irrelevant background information. This network will identify the probability of the presence of each organ. The extracted regions will be fed to the attention deeplab3 to generate a fine segmentation. Images of 480 patients (360 EBRT and 120 brachytherapy) with prostate cancer were utilized in this study. The performance of the proposed framework was evaluated through well established quantitative metrics such as Dice similarity coefficient (DSC), and Hausdorff distance (HD). PD-0409 cascade-net: a deep learning framework for segmentation of prostate and organs at risk in CT images Z. Siavashpour 1 , E. Showkatian 2