ESTRO 2020 Abstract book

S63 ESTRO 2020

Gy (37.5 Gy) prescribed on the 80% isodose over 9 days. RT was delivered with a Cyberknife M6 while the tracking was based on 2 pairs of linked fiducial markers in the prostate. 1.5-T MRI was performed at diagnosis for contouring and at 3-year follow up to confirm the resolution of the initial nodules. Toxicities were scored using the CTCAEv4 and quality of life (QOL) with IPSS and IEFF5 scores. Biochemical control follows the Phoenix definition. The preliminary results of the first 73 patients with a median follow-up of 36 months are presented. According to the binomial law with an assumption of <5% risk of severe toxicity, 73 patients is the minimum number of patients with no severe toxicity required to demonstrate the safety of this technique in a larger amount of patients with a 95% confidence interval. Results No early nor late grade > 3 toxicity was observed. 19.2% of patients complained of late grade 1-2 toxicity (2 grade 2 (2,7%) proctitis, 1 grade 2 (1,4%) dysuria). Mean urinary QOL at baseline and at the end of follow up were 1.23 ± 1.12 and 0.83 ± 0.94 respectively (p>0.05). Mean IPSS at baseline and at the end of follow up were 4.26 ± 4.35 and 3.53 ± 2.72 (p>0.05). 3-year biochemical control were respectively 100%, 92.5% and 54.5% considering low, intermediate and high risk prognosis. 5 patients suffered from clinical recurrence with 2 local, 4 nodal and 2 metastatic recurrences. MRI complete response at 3 years was 96.7% (29/30) for the 30 first patients with a complete 3-year-follow-up. As no severe toxicity was observed at 36 months in this population, according to the binomial law, we conclude to the safety of our method at a 95% confidence interval (p<0.05). Conclusion Preliminary results are encouraging. SBRT as a short treatment offers a safe and convenient treatment modality, while reducing costs, and could also challenge watchful waiting policies. Using the binomial law in this trial allows us to demonstrate the safety of prostatic SBRT based on preliminary results. We propose this statistical approach to boost clinical implementation of new technologies in radiation treatments while offering the best safety to patients in the ongoing trials. PH-0117 Radiotherapy of T4M0 prostate cancer : A multicentric retrospective analysis F. Goupy 1 , E. Meyer 2 , P. Pommier 3 , N. Magné 4 , P. Sargos 5 , D. Pasquier 6 , G. Noël 7 , U. Schick 8 , A. Hasbini 9 , S. Supiot 10 , A. Bossi 11 , I. Latorzeff 12 , J. Riverain 2 , L. Duvergé 3 , M. Benna 4 , N. Benziane 5 , T. Le Roy 6 , C. Bigot 7 , M. Rehn 8 , L. Vaugier 10 , B. Le Proust 13 , A. Barateau 14 , B. Campillo- Gimenez 15 , J. Castelli 16 , R. De Crevoisier 16 1 CLCC Eugène Marquis, Radiation Department, Rennes F- 35000, France ; 2 CLCC François Baclesse, Radiation Department, Caen F-14000, France ; 3 CLCC Léon Bérard, Radiation Department, Lyon F-69000, France ; 4 Institut de Cancérologie Lucien-Neuwirth, Radiation department, Saint-Priest-en-Jarez F-42271, France ; 5 CLCC Institut Bergonié, Radiation Department, Bordeaux F-33000, France ; 6 CLCC Oscar Lambret, Radiation Department, Lille F-59000, France ; 7 CLCC Paul Strauss, Radiation department, Strasbourg F-67000, France ; 8 University Hospital Cavale Blanche, Radiation department, Brest F- 29200, France ; 9 Centre Finistérien de Radiothérapie et d'Oncologie, Radiation department, Brest F-29200, France ; 10 CLCC Institut de Cancérologie de l’Ouest, Radiation department, Saint-Herblain F-44800, France ; 11 Institut Gustave Roussy, Radiation department, Villejuif F-94800, France ; 12 Clinique Pasteur, Radiation department, Toulouse F-31076, France ; 13 CLCC Eugène Marquis, Radiation Medical Imaging Department, Rennes F-35000, France ; 14 University Rennes 1- LTSI Laboratoire Traitement du Signal et de l'Image, Inserm U1099, Rennes F-35000, France ; 15 CLCC Eugène Marquis, Clinical Research Direction, Rennes F-35000, France ; 16 CLCC Eugène Marquis, Radiation Department- University

PH-0115 Five-year outcomes of 51.6 Gy (RBE) in 12- fractionated carbon-ion RT for localized prostate cancer H. Sato 1 , G. Kasuya 2 , T. Chang 2 , H. Makishima 2 , K. Nemoto 1 , H. Tsuji 2 1 Yamagata University Faculty of Medicine, Radiation Oncology, yamagata, Japan ; 2 QST Hospital- National Institutes for Quantum and Radiological Science and Technology, Radiation Oncology, Chiba, Japan Purpose or Objective Although 51.6 Gy (relative biological effect [RBE]) in carbon-ion radiotherapy (CIRT) at 12 fractions over a 3- wk period has been performed since 2010 and is now regarded as standard CIRT treatment, there is no report of clinical outcomes with long-term follow-up after CIRT using the dose prescription. This retrospective analysis determined the post-CIRT clinical outcomes of patients treated at our institution at the dose prescription with a >5-year median follow-up. Material and Methods A total of 321 patients with localized prostate cancer who received CIRT at 51.6 Gy (RBE) in 12 fractions in one of two protocols (1002 and 9904-4) between July 2010 and February 2014 were analyzed. Biochemical relapse-free survival (BRFS) defined per the Phoenix definition and the survival rates were calculated. The incidence of acute and late adverse events was evaluated based on the Common Terminology Criteria for Adverse Events ver. 4.0. Results The numbers of low-, intermediate-, and high-risk group patients were 49 (15%), 130 (41%), and 142 (44%), respectively. The median follow-up period of the surviving patients was 5.1 years (range, 1.1–8.5 years). The 5-year BRFS rates of the low-, intermediate-, high-risk groups were 95.7%, 92.2%, and 92.6%, respectively. The disease-specific survival of the entire group was 100%. Acute (n=0) and late (n=2; 0.6%) G2 gastrointestinal (GI) toxicities were observed. Acute (n=19; 5.9%) and late (n=4; 1.2%) G2 genitourinary (GU) toxicities occurred, including the acute (n=1; 0.3%) and late (n=1; 0.3%) G2 hematuria. None ≥G3 toxicities were observed. Conclusion The 12-fractionated CIRT at 51.6 Gy (RBE) for localized prostate cancer was effective and showed low toxicity. PH-0116 Stereotactic radiotherapy for prostate cancer: preliminary results of a phase II prospective trial V.P. Nguyen 1 , H. Alzin 2 , L. Celine 1 , L. Harzée 3 , S. Joseph 3 , M. Untereiner 1 , B. Frédérick 1 , S. Biver 1 , Z. Bodgal 1 , S. Philippi 1 , P. Nickers 1 1 Centre François Baclesse, Radiotherapy Department, Esch-sur-Alzette, Luxembourg ; 2 Kirchberg Hospital, Urology, Luxembourg, Luxembourg ; 3 Centre François Baclesse, Physics Department, Esch-sur-Alzette, Luxembourg Purpose or Objective Data from phase III prospective trials comparing more conventional RT and SBRT are awaited while the use of SBRT is increasing by extrapolating the results of HDR Brachytherapy. Toxicity and QOL remain the major factors to determine a treatment modality in prostate cancer especially in older patients since until now overall survival was not improved with moderate or extreme hypofractionnation. Our preliminary results and methodology using the binomial law to monitor the safety during such a trial are presented. Material and Methods 150 patients > 70 years were prospectively and consecutively included in a phase II trial from 4/2014- 7/2018 (NCT03235557). Low (CAPRA 0-2) and Intermediate (CAPRA 3-5) risk patients received 5 fractions of 7.25 Gy (36.25 Gy), and High risk (CAPRA 6-10) 5 fractions of 7.5

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