Abstract Book

S846

ESTRO 37

Purpose or Objective Image guided intensity modulated radiotherapy (IG-IMRT) enables dose escalation, while minimizing the treatment related toxicities in the management of carcinoma prostate. Localization using gold markers and online treatment verification could potentially reduce the planning target volume (PTV) which may translate in to reduction of radiation toxicity. We aim to retrospectively evaluate the effect of PTV reduction on acute as well as late radiation toxicity and compare the biochemical control. Material and Methods The present study is a single institution retrospective evaluation. Histopathologically proven adenocarcinoma of prostate, T1c-T3bN0M0, age ≥ 18 years, karnofsky performance status (KPS) of ≥70 treated definitively with RT were evaluated. Patients were staged as per AJCC 7 th and risk stratification done by the D’Amico criteria. A week prior to simulation, 3 fiducial gold markers were inserted under transrectal ultrasound guidance. Contrast enhanced computed tomography planning scan was done with bladder and rectal protocol. In PTV_7 arm, PTV expansion of 7 mm, except posterior (6mm) was given on high risk clinical target volume (HR-CTV) to obtain the respective HR-PTV. While in PTV_5 arm, isotropic expansion of 5 mm was used. 7 mm margin was given to low risk CTV (which included nodal volumes) for LR-PTV in both groups. 78 Gray (Gy)/39 fractions @ 2 Gy/fraction was delivered in 2 phases. In 1 st phase 46 Gy to both HR and LR-PTV was delivered followed by boost of 32 Gy to HR-PTV. Patients were evaluated weekly and acute toxicities were graded as per CTCAE 4.03. Late toxicities were graded as per RTOG late morbidity criteria. Biochemical failure was defined as per phoenix consensus guideline. Results Between Nov 2013 and July 2017, 50 patients were evaluated (25 in each arm). Median age was 68 years (60- 82), median KPS was 80 with 44/50 high risk patients.At a median follow up of 37 months(11-76), overall late gastrointestinal (GI) toxicity at 3 year was 72%, 18% and 10% for grade 1, 2 and 3 respectively and genitourinary (GU) toxicities were 68%, 24% and 8% for grade 1, 2 and 3 respectively. In PTV_7 group the grade ≥3 chronic GI toxicities were significantly higher compared to PTV_5 group [10% vs. 0%, p=0.05] and non-significant difference in grade ≥3 chronic GU toxicities [6% vs. 2%, p=0.6]. The acute RT toxicities in terms of proctitis [40% vs 12%, OR- 4.8, p=0.05] were significantly higher in PTV_7 arm compared to PTV_5 arm. 3 year overall biochemical progression free survival (B-PFS) rates were 95% [100% (PTV_7) vs. 90% (PTV_5), p= 0.69]. The 3 year overall survival (OS) rates were 94 % vs. 88%, p=0.39. Conclusion PTV reduction can be safely used with dose escalated radiotherapy while using marker based IG-IMRT with daily verification. This may result in reduction of chronic GI toxicity without compromising on biochemical control. Further prospective studies are warranted in this regard. EP-1570 Salvage SBRT for local recurrence of prostate cancer after definitive radiotherapy D. Lam Cham Kee 1 , J. Doyen 1 , A. Falk 1 , J.M. Hannoun- levi 1 1 centre antoine lacassagne, radiotherapy, nice, France Purpose or Objective Prostate cancer local recurrence (PCLR) after definitive irradiation (external beam and/or brachytherapy) can be

considered for local treatment in EAU-ESTRO-SIOG guidelines such as surgery, cryotherapy, high intensity ultra-sound or brachytherapy. We therefore performed a literature review of the role of stereotactic body radiation therapy (SBRT) in re-irradiation of PCLR. Material and Methods We performed a MEDLINE/MeSH research in September 2017, using the key words: SBRT, prostate cancer, local recurrence, salvage, biochemical relapse, re-irradiation. Only English articles concerning PCLR alone were reviewed. Results From 2010 to 2017, 9 articles were found (including one case report). The total number of patients (pts) was 156, with a global median follow-up of 15.7 months [range: 10 - 22.6 months]. The treatment was performed at a median time interval between primary treatment and salvage re-irradiation of 88 months [range: 13.5 – 126 months]. The main machine used was CyberKnife and the median prescribed dose was 32 Gy [range: 25 - 36.25 Gy] in 5 fractions. Seventy-one patients (45.5%) underwent Androgen deprivation therapy combined with salvage SBRT. The efficacy results were heterogeneous and the main end point used was 2 nd biochemical relapse defined using the Phoenix criteria. Toxicity results of grade 3 or higher using CTCAE evaluation were low (no gastro- intestinal toxicity versus 2% of acute and late urinary toxicity). Conclusion SBRT seems to be a safe salvage treatment for PCLR. Its long-term efficacy and toxicity as well as optimal total dose and dose per fraction remains to be determined by further studies. EP-1571 Is Neoadjuvant ADT Necessary for Intermediate-Risk Prostate Cancer Treated with Proton Therapy? M. Takagi 1 , Y. Demizu 2 , N. Fuwa 2 , N.S. Sulaiman 2 , K. Terashima 2 , O. Fujii 3 , D. Jin 4 , F. Nagano 2 , T. Waki 4 , M. Mima 2 , Y. Niwa 4 , K. Katsui 5 , M. Murakami 6 , T. Okimoto 2 1 Sapporo Teishinkai Hospital, Proton Therapy Center, Sapporo, Japan 2 Hyogo Ion Beam Medical Center, Department of Radiology, Tatsuno, Japan 3 Hakodate Goryoukaku Hospital, Department of Radiation Oncology, Hakodate, Japan 4 Tsuyama Chou Hospital, Department of Radiology, Tsuyama, Japan 5 Okayama University, Department of Radiology, Okayama, Japan 6 Southern Tohoku General Hospital, Proton Therapy Center, Koriyama, Japan Purpose or Objective Presently no prospective, randomized trials have clearly defined the role of neoadjuvant androgen-deprivation therapy (N-ADT) for patients with intermediate-risk prostate cancer with proton therapy (PT). In this study, we assessed the impact of adding N-ADT to PT on A total of 600 patients with intermediate-risk prostate cancer (any of the 3 risk factors: PSA 10-20 ng/mL, Gleason Score (GS): 7, T2b-T2c) treated with PT at Hyogo Ion Beam Medical Center from 2001 to 2014 were included in this study. By the following methods, whether N-ADT improved freedom from biochemical failure (FFBR) of the intermediate-risk patients was investigated. 1) Prognostic factor analysis including N-ADT for all biochemical control. Material and Methods