ESTRO 2022 - Abstract Book

S1199

Abstract book

ESTRO 2022

PO-1414 Results of a concept-development for a phase III trial on radiotherapy in primary prostate cancer

S. Spohn 1,2 , S. Adebahr 1 , M. Huber 3 , C. Jenkner 3 , R. Wiehle 4 , B. Nagavci 5 , C. Schmucker 6 , E. Carl 7 , R. Chen 8 , W. Weber 9 , M. Mix 10 , A. Rühle 1 , N. Nicolay 1 , C. Gratzke 11 , M. Benndorf 12 , T. Wiegel 13 , J. Weis 14 , D. Baltas 4 , C. Zamboglou 1,2,15 , A. Grosu 1 1 University Medical Center Freiburg, Department of Radiation Oncology, Freiburg, Germany; 2 Faculty of Medicine, Berta- Ottenstein-Programme, Freiburg, Germany; 3 Faculty of Medicine and Medical Center, Clinical Trials Unit, Freiburg, Germany; 4 University Medical Center Freiburg, Division of Medical Physics - Department of Radiation Oncology, Freiburg, Germany; 5 University Medical Center Freiburg, Institute for Evidence in Medicine, Freiburg, Germany; 6 University Medical Center, Institute for Evidence in Medicine, Freiburg, Germany; 7 Bundesverband Prostatakrebs Selbsthilfe e.V., Bundesverband Prostatakrebs Selbsthilfe e.V., Bonn, Germany; 8 University of Kansas Cancer Center, Department of Radiation Oncology, Kansas City KS 5, USA; 9 Klinikum rechts der Isar - Technical University of Munich, Department of Nuclear Medicine, Munich, Germany; 10 University Medical Center Freiburg, Department of Nuclear Medicine, Freiburg, Germany; 11 University Medical Center Freiburg, Department of Urology, Freiburg, Germany; 12 University Medical Center Freiburg, Department of Radiology, Freiburg, Germany; 13 University Hospital Ulm, Department of Radiation Oncology, Ulm, Germany; 14 Comprehensive Cancer Center - University Medical Center Freiburg, Department of Cancer Self-Help Research, Freiburg, Germany; 15 European University of Cyprus, German Oncology Center, Limassol, Cyprus Purpose or Objective Failure rate in randomized controlled trials (RCTs) is > 50%, includes safety-problems, underpowered statistics, lack of efficacy, lack of funding or insufficient patient recruitment and is even more pronounced in oncology trials. We present results of a structured concept-development phase (CDP) for a phase III RCT on personalized radiotherapy (RT) in primary prostate cancer (PCa) patients implementing prostate specific membrane antigen targeting positron emission tomography (PSMA-PET). Materials and Methods The one year process of the CDP contained five main working packages: (i) literature search and scoping review, (ii) involvement of individual patients, patients’ representatives and patients’ self-help groups addressing the patients’ willingness to participate in the preparation process and the conduct of RCTs as well as the patient informed consent (PIC), (iii) involvement of national and international experts and expert panels (iv) a phase II pilot study investigating the safety of implementation of PSMA-PET for focal dose escalation RT and (v) in-silico RT planning studies assessing feasibility of envisaged dose regimens and effects of urethral sparing in focal dose escalation. Results (i) Systematic literature searches confirmed the high clinical relevance for more evidence on advanced RT approaches, in particular stereotactic body RT, in high-risk PCa patients. (ii) Involvement of patients, patient representatives and randomly selected males relevantly changed the PIC and initiated a patient empowerment project for training of bladder preparation. (iii) Discussion with national and international experts led to adaptions of inclusion and exclusion criteria. (iv) Fifty patients were treated in the pilot trial and in- and exclusion criteria as well as enrollment calculations were adapted accordingly. Parallel conduction of the pilot trial revealed pitfalls on practicability and broadened the horizon for translational projects. (v) In-silico planning studies confirmed feasibility of envisaged dose prescription. Despite large prostate- and boost-volumes of up to 66% of the prostate, adherence to stringent anorectal dose constraints was feasible. Urethral sparing increased the therapeutic ratio. Conclusion The dynamic framework of interdisciplinary working programs in CDPs enhances robustness of RCT protocols and may be associated with decreased failure rates. Structured recommendations are warranted to further define the process of such CDPs in radiation oncology trials. C. Rosa 1,2 , M. Borgia 1 , M. Lucarelli 1 , D. Fasciolo 1 , A. Vinciguerra 1 , A. Augurio 1 , S. Marcucci 1 , L. Caravatta 1 , M. Marchioni 3 , M. Di Nicola 3 , D. Genovesi 1,2 1 SS. Annunziata Hospital, Department of Radiation Oncology, Chieti, Italy; 2 G. D’Annunzio University, Department of Neuroscience, Imaging and Clinical Sciences, Chieti, Italy; 3 G. D'Annunzio University, Laboratory of Biostatistics, Department of Medical, Oral and Biotechnological Sciences, Chieti, Italy Purpose or Objective Purpose: In prostate cancer (PC) patients set-up errors can vary the prostate position between a planned Computed Tomography (CT) and Cone Beam CTs (CBCT) performed during radiotherapy (RT). Furthermore, pelvic organ motions with bladder and rectum filling variations could emphasize the variation in position of the prostate. Our aim is the evaluation of inter-fraction prostate motion, in empty rectum and controlled bladder filling, on planned-CT and CBCT. Materials and Methods Material and Methods: We retrospectively evaluated thirty-three PC patients analyzing the first daily CBCTs performed in the first four days of RT, calculating the average shifts in all the three axes (x, y and z) and then repeating CBCT once a week after the correction of these prostate shifts. For each patient, we evalued rectum and bladder volumes on each planned-CT and CBCT. We calculated the median shift variations on all three axes and rectum and bladder filling variations between planned-CT and CBCTs on the first four CBCTs, on the following weekly CBCTs and for the total of CBCTs. Linear regression mixed models taking into account the random effect of repeated measures were employed, to identify correlation between median prostate shifts and rectum and bladder filling variations. PO-1415 Inter-fraction error analyses and rectal and bladder volume variations using CBCT in prostate cancer