Abstract Book

ESTRO 37

S427

Partner Site Freiburg- German Cancer Research Center DKFZ- Heidelberg- Germany, Freiburg, German Purpose or Objective To evaluate the oncological and treatment-related toxicity outcomes after combined high-dose-rate (HDR) brachytherapy with external beam radiotherapy (EBRT) for patients with clinically localized prostate cancer. Material and Methods Between 2008 and 2012, 314 consecutive patients with intermediate- and high-risk localized prostate cancer were treated with two fractions of HDR brachytherapy followed by supplemental EBRT. The HDR brachytherapy boost consisted of two single-fraction implants at 10.5 Gy per fraction delivered to an intraoperative real-time, transrectal ultrasound defined planning treatment volume up to a total physical dose of 21.0 Gy. The conventionally fractionated EBRT delivered additional 45.0 Gy to the prostate gland and seminal vesicles. Biochemical failure was defined according to the Phoenix Consensus Criteria and genitourinary (GU)/gastrointestinal (GI) toxicity evaluated using the Common Toxicity Criteria for Adverse Events version 3.0. Results The median follow-up was 71.7 months. The 6-year overall survival, biochemical control and metastasis-free- survival rates for the entire cohort and among high-risk patients were 88.7 %, 86.3 %, 94.0 % as well as 88.3 %, 85.7 % and 93.8 %, respectively. Androgen deprivation therapy was initiated prior to treatment in 93 % of patients. Toxicity was scored per event with late Grade 2, 3 and 4 GU adverse events of 15.3 %, 2.1 % and 0.3%, respectively. Late Grade 2 GI toxicity amounted 0.6 % with no instances of Grade 3 or higher late adverse events to be reported. Conclusion High-dose-rate BRT with supplemental EBRT results in very encouraging biochemical relapse-free survival rates with a low incidence of severe late GU or GI toxicities. PO-0820 The bowel syndrome after whole pelvis RT for prostate cancer: acute symptoms and quality of life B. Noris Chiorda 1 , P. Gabriele 2 , F. Munoz 3 , E. Garibaldi 2 , F. Migliaccio 4 , A. Faiella 5 , C. Giordano 5 , D. Cante 6 , E. Petrucci 7 , B. Avuzzi 8 , T. Giandini 9 , E. Villa 10 , P. Salmoiraghi 11 , G. Girelli 12 , B. Farina 13 , J. Waskiewicz 14 , P. Farina 15 , M. Gaetano 16 , V. Carillo 17 , V. Sacco 1 , C. Bianconi 1 , F. Badenchini 18 , C. Fiorino 19 , T. Rancati 18 , C. Cozzarini 1 1 IRCCS San Raffaele Scientific Institute, Radiotherapy, Milan, Italy 2 Istituto di Candiolo- Fondazione del Piemonte per l'Oncologia IRCCS, Radiotherapy, Candiolo Torino, Italy 3 Ospedale Regionale U.Parini-AUSL Valle d’Aosta, Radiotherapy, Aosta, Italy 4 Ospedale Regionale U.Parini-AUSL Valle d’Aosta, Medical Physics, Aosta, Italy 5 Istituto Nazionale dei Tumori “Regina Elena”, Radiotherapy, Rome, Italy 6 Ospedale di Ivrea- A.S.L. TO4, Radiotherapy, Ivrea, Italy 7 Ospedale di Ivrea- A.S.L. TO4, Medical Physics, Ivrea, Italy 8 Fondazione IRCCS Istituto Nazionale dei Tumori, Radiotherapy, Milan, Italy 9 Fondazione IRCCS Istituto Nazionale dei Tumori, Medical Physics, Milan, Italy 10 Cliniche Gavazzeni-Humanitas, Radiotherapy, Bergamo, Italy 11 Cliniche Gavazzeni-Humanitas, Medical Physics, Bergamo, Italy 12 Ospedale degli Infermi, Radiotherapy, Biella, Italy 13 Ospedale degli Infermi, Medical Physics, Biella, Italy 14 Comprensorio Sanitario di Bolzano, Radiotherapy, Bolzano, Italy

and –PET). Isotropic expansion by 4 mm resulted into the respective planning target volumes (PTVs). For each of these PTVs two plans were generated. Plan95 consisted of whole-prostate IMRT to 77 Gy in 35 fractions and a simultaneous boost to 95 Gy (Plan95 PET /Plan95 MRI /Plan95 union ). Plan80 consisted of whole-prostate IMRT to 76 Gy in 38 fractions and a simultaneous boost to 80 Gy (Plan80 PET /Plan80 MRI /Plan80 union ). TCPs were calculated for GTV-histo (TCP-histo), which was delineated based on the PCa distribution in co-registered histology slices. NTCPs were assessed for bladder and rectum. Results Mean GTV-histo, GTV-PET, GTV-MRI and GTV-union amounted to 15±12 %, 17±13 %, 10±9 % and 20±14 % of the total prostatic volume (mean 54.2±24.4 ml), respectively. In average, 86±10 %, 74±17 % and 93±5 % of GTV-histo overlapped with PTV-PET, PTV-MRI and PTV- union, respectively. For all patients the target volume objectives as well as the OAR dose constraints were met (according to FLAME trial protocol and Pinkawa et al.). TCP-histo values are listed in Table 1. For Plan95 union higher TCP-histo values were calculated than for Plan95 MRI (p=0.008) and Plan95 PET (p=0.008). Plan80 union had significantly higher TCP-histo values than Plan80 MRI (p=0.012), but not than Plan80 PET (p=0.472). Whether the dose escalation was delivered based on mpMRI or PSMA PET information had no impact on TCP-histo values for both protocols (p>0.05). NTCP calculations for bladder and rectum reached no significant differences for all plans (p>0.05), with the exception that Plan95 MRI had significantly lower NTCP-rectum values than Plan95 union (p=0.012) and Plan95 PET (p=0.047), respectively. Conclusion The concept of an IMRT focal dose escalation based on GTVs delineated by combined PSMA PET and mpMRI information was feasible and achieved high TCP-histo values with acceptable NTCPs in our planning study. These findings should be further validated in a prospective IMRT or brachytherapy dose escalation trial for patients with primary PCa. PO-0819 High dose rate brachytherapy plus external beam radiotherapy for localized prostate cancer I. Strouthos 1 , G. Chatzikonstantinou 2 , N. Tselis 2 , N. Milickovic 3 , S. Papaioannou 3 , S. Butt 3 , A.L. Grosu 4 , D. Baltas 5 , N. Zamboglou 2 1 Medical Center - University of Freiburg, Department of Radiation Oncology, Freiburg, Germany 2 J.W. Goethe University, Department of Radiotherapy and Oncology, Frankfurt am Main, Germany 3 Sana Klinikum Offenbach, Department of Medical Physics and Engineering, Offenbach am Main, Germany 4 Medical Center- Faculty of Medicine- University of Freiburg, Department of Radiation Oncology- German Cancer Consortium DKTK Partner Site Freiburg- German Cancer Research Center DKFZ- Heidelberg- Germany, Freiburg, Germany 5 Medical Center- Faculty of Medicine - University of Freiburg, Division of Medical Physics - Department of Radiation Oncology- German Cancer Consortium DKTK Table 1. TCP-histo values Plan9 5 PET Plan9 5 MRI Plan95 u nion Plan8 0 PET Plan8 0 MRI Plan80 u nion Mean (%) 94.7 96.9 99.7 73.0 70.8 75.5 Maxim um (%) 100.0 100.0 100.0 94.0 94.0 95.2 Minim um (%) 69.6 86.4 97.4 25.1 30.2 33