ESTRO 37 Abstract book

ESTRO 37

S575

MRI guided biopsy. They result in a map of cancer distribution within different parts of the gland. There are at least several commercially available software systems to guide TRUS-MRI fusion biopsy. Unfortunately their cost exceeds the financial abilities of many brachytherapy departments. The goal of this study was to check the feasibility of TRUS-MRI fusion prostate biopsy using ONLY brachytherapy TPS. Material and Methods From 12.2016 to 09.2017 we performed TRUS-MRI fusion biopsies of prostate in 27 pts. The main indications for this procedure were: repeat biopsy after previously negative biopsy (14pts), suspicion of local recurrence of PCa after EBRT (8pts), other (4pts). The median age was 72 (51-84) yo. The median PSA level was 9,5 (2,13- 170) ng/ml. We defined 35 suspected lesions on MRI images. 6 lesions were scored PIRADS3, 13- PIRADS4, 7- PIRADS5, 9- were not scored with PIRADS (pts with suspicion of radio- recurrent tumors). MRI images were analyzed with Oncentra Brachy TPS (Elekta AB). In this system we also delineated prostate, suspected lesions and 5mm margins for every lesion. Prepared images were subsequently sent to Oncentra Prostate TPS (Elekta AB). This system was used to perform TRUS-MRI fusion transperineal biopsy with following steps: 1. acquisition of 3D TRUS images of prostate; 2. fusion of MRI and TRUS images; 3. preplanning of the desired position of biopsy cores; 4. guidance of targeted biopsy, biopsy of 5mm margin, systematic biopsy of left and right lobe. Each biopsy core was named with template position and sent separately to Pathology Department. All data from pathology report were entered into Oncentra Prostate TPS resulting in 3D map of cancer distribution within the gland. Results We obtained verification of PCa in 88% pts. The median volume of lesion was 0,53 (0,1-8,4) cc, of lesion with 5mm margin 2,95 (2-22) cc. The median number of biopsy cores was 22 (17-27). From 35 lesions 57,6% were positive for PCa, with PIRADS3, 4, 5 and no PIRADS lesions being positive in 16,6%, 58,3%, 71,4% and 66% of cases, respectively. Among pts with PCa verification 31,8% were positive only within lesion, 59% within lesion and 5mm margin, 68,2% within lesion, margin and occupied lobe. If biological significance of PCa was added to this analysis the above-mentioned values changed to 41%, 68,1% and 77,3%, respectively. Only in 5 pts biologically significant cancer outside occupied lobe was found. One patient experienced major toxicity (AUR). Conclusion Transperineal TRUS-MRI fusion prostate biopsy is feasible with the use of brachytherapy TPS which are available at the majority of cancer centres. There is no need for extra expenses related to commercially available systems. We hope this study will help brachytherapy community to move towards focal treatment in selected pts with PCa. PO-1025 Effects of antecedent androgen deprivation therapy in prostate seed implant brachytherapy dosimetry R. Nakamura 1 1 Iwate Medical Univerrsity, Department of Radiology, Morioka, Japan Purpose or Objective Seed implant brachytherapy (BT) for organ-confined prostate cancer (OCPC) is frequently combined with androgen deprivation therapy (ADT) to enhance control of unfavorable disease. It is believed that antecedent ADT

Conclusion This study shows that the source trajectory can be determined accurately using an IP. The default TPS model could be improved by shifting the dwell positions by 3mm towards the channel tip. The mean and maximum error then equal our modified model. In the future, we want to repeat these experiments to verify the results are consistent in time. Furthermore, we want to derive the 3D source trajectory using the IP signal intensity. The simplification that the source is always at the center of the source channel might be a robust solution when the snaking pattern is not consistent in time. PO-1024 Transperineal TRUS-mpMRI fusion prostate biopsy using brachytherapy treatment planning systems ONLY. M. Dabkowski 1 , E. Gruszczynska 2 , A. Lewicki 3 , J. Palucki 4 , M. Durzynska 5 , A. Kulik 1 , M. Szymanski 6 , W. Rogowski 7 , A. Kasprowicz 1 1 The Maria Sklodowska-Curie Memorial Cancer Center, Department of Brachytherapy, Warsaw, Poland 2 The Maria Sklodowska-Curie Memorial Cancer Center, Department of Physics, Warsaw, Poland 3 Centre of Postgraduate Medical Education, Urology Clinic, Warsaw, Poland 4 The Maria Sklodowska-Curie Memorial Cancer Center, Department of Radiology, Warsaw, Poland 5 The Maria Sklodowska-Curie Memorial Cancer Center, Department of Pathology, Warsaw, Poland 6 The Maria Sklodowska-Curie Memorial Cancer Center, Urology Clinic, Warsaw, Poland 7 Central Clinical Hospital of the MSWiA, Urology Clinic, Warsaw, Poland Purpose or Objective Focal prostate brachytherapy (FPB) is an emerging treatment modality for selected PCa pts. The requirements for high-quality FBP are mpMRI and TRUS- Poster: Brachytherapy: Prostate