ESTRO 38 Abstract book

S829 ESTRO 38

analyse the influence of obesity in treatment outcomes with high doses of external beam radiation therapy (HDEBRT) plus androgen deprivation therapy (ADT) in patients (pts) with prostrate cancer (PC) treated with radical intention. Material and Methods Material/methods : Retrospective comparative study of 297 out of 531 pts with PC treated with EBRT+ADT in our hospitals from October 2001 to December 2011 with height and weight data available at baseline (56%). 168 were non-obese (57%) and 129 obese (43%). Baseline characteristics non-differed significantly between treatment groups in PSA level, tumour stage, risk group, percentage of positive cylinder, ADT duration and total dose of RT but more obese pts had cardiovascular events, high blood pressure an metabolic alterations. All pts were treated with 3DCRT at a median total dose of 78 Gy (range 74-78). Phoenix definition was used for biochemical failure. Survival rates were estimated with Kaplan-Meier and compared with Log Rank test. Prognostic factors such as age, primary tumour stage, Risk group, Gleason, percentage of positive cylinder, radiotherapy total dose and ADT duration have been related to BDFS, OS and PCSS using Cox regression. Results Results : The median follow-up was 84 months (range 11- 175) in non-obese pts and 91 months (range 29-188) in obese pts.The 7-year BDFS, OS and PCSS in non-obese pts were 92,4%, 91,6%, and 99.9% respectively and in obese were 88.2% (p=0.147), 90.1% (p=0.384), and 96.6% (p=0.330) respectively. In the multivariate analysis, obesity was not a significant prognostic factor of BDFS, OS neither PCSS. Conclusion Conclusion : Regarding to our results, obesity in prostate cancer treated with high doses of EBRT did not have significantlyinfluence in BDFS, OS and CSS. Studies with large sample of pts are recommended EP-1537 Local Relapse after Radiotherapy for prostate cancer: is a second local treatment worthwhile? C. Hennequin 1 , M. Pierre 2 , D.K. Eric 3 , V. Laetitia 4 , D. François 2 , C. Stephane 5 , Q. Laurent 1 1 Hôpital Saint-Louis- AP-HP, Radiation Oncology, Paris, France ; 2 Hôpital Saint-Louis- AP-HP, Urology, Paris, France ; 3 Hôpital Saint-Louis- AP-HP, Radiology, Paris, France ; 4 Hôpital Saint-Louis- AP-HP, Nuclear Medicine, Paris, France ; 5 Hôpital Saint-Louis- AP-HP, Medical Oncology, Paris, France Purpose or Objective To compare the outcome of patients with an isolated local relapse (LR) after radiotherapy (RT) of prostate cancer treated with a salvage local treatment (SLT) with those only monitored Material and Methods Between January 2011 and December 2016, all consecutive patients presenting a biochemical relapse (BR: nadir+2ng/ml) after RT (external beam radiotherapy or brachytherapy) who had a staging including a 18- fluorocholine-PET-CT (FCH-PET/CT) were prospectively registered. Patients with an isolated LR had systematically a multiparametric magnetic resonance imaging (mpMRI) to confirm LR. After evaluation of comorbidities, life expectancy, functional status and discussion with the patient, a SLT (cryotherapy, stereotactic RT: SBRT or High-Intensity Focused Ultrasounds: HIFU) or a simple surveillance could be proposed. A salvage androgen deprivation therapy (ADT) was given in case of a PSA doubling-time ≤ 12 months or a PSA level higher than 10 ng/ml or if distant metastases are detected. Results Among the 134 patients with a BR, 67 had an isolated LR on FCH-PET/CT and mpMRI. Mean age was 67 yrs (53-86). Initial prognostic groups was: favourable: 20;

Orsola-Malpighi Hospital, Bologna, Italy ; 4 Radiotherapy Unit, Fondazione di Ricerca e Cura “Giovanni Paolo II", Campobasso, Italy ; 5 Medical Physics Unit, Fondazione di Ricerca e Cura “Giovanni Paolo II", Campobasso, Italy ; 6 Medical Physics Unit, Dept. of Experimental- Diagnostic and Specialty Medicine - DIMES- University of Bologna- S. Orsola-Malpighi Hospital, Bologna, Italy ; 7 Department of Radiotherapy, Policlinico Universitario “A. Gemelli”- Università Cattolica del Sacro Cuore, Rome, Italy Purpose or Objective New evidences suggested a vascular etiology for sexual impotence after prostate radiotherapy. Internal pudendal arteries (IPA), corpora cavernosa (CC) and penile bulb (PB) were identified as critical structures related to erectile function. We explored the potential of VMAT to spare the critical erectile structures with a SIB to the dominant intraprostatic lesion (DIL) Material and Methods Twelve patients were selected for this study. DILs were defined using T2-weighted, dynamic contrast-enhanced and diffusion-weighted MRI (multiparametric MRI). Vascular structures were contoured and expanded by a uniform 2 mm margin. The seminal vescicles, the prostate and DIL were expanded uniformly by 5 mm to create the planning target volumes (PTVsv, PTVpr and PTVdil, respectively). PTVsv, PTVpr and PTVdil dose prescription was 56.25, 67.50 and 75 Gy, respectively, in 25 fractions. The doses were prescribed to cover >95% of PTVs. All VMAT plans were generated in a dual-arc modality for a VersaHD linac. Original clinical plans (ST-VMAT) were created to fulfil targets coverage and Quantec constraints for non vascular OARs (NV_OARs: rectum, bladder and femoral heads). For each patient, a new plan (SS-VMAT) based on the approved ST-VMAT plan was created. IPA, CC and PB were considered OARs related to sexual impotence (V_OARs). All objectives for PTVs coverage and NV_OARs sparing were left unchanged. New objectives were added for V_OARs, with priority to minimize mean doses to IPA, CC and PB. A Wilcoxon signed-rank test was used to compare the two optimization techniques. Results For all plans, targets coverage was well within the predefined objectives for all metrics (D95, D98, Dmean). In particular, D98% was >95% of prescribed doses for all targets, patients and techniques. No significant differences were found in sparing rectum, bladder and femoral heads for all considered metrics (Dmean, V50, V60, V70). With regard to V_OARs sparing, SS_VMAT plans provided a major reduction of dose irradiation. Mean doses for IPA, CC and PB were reduced by 32.4% (11.2 Gy, p=0.002), 22.5% (4.1 Gy, p=0.006) and 10.0% (4.6 Gy, p=0.010), respectively. V30 decreased from 61.1% to 21.4% (p=0.02) for IPA and from 27.2% to 14.8% (p=0.04) for CC. Conclusion We showed that a significant dose sparing for IPA, CC and PB using VMAT-SIB strategy is feasible, allowing vessel- sparing and highly conformal plans, dose escalation to DIL and fast treatment delivery. EP-1536 Influence of obesity in treatment outcomes in prostate cancer patients J.L. Munoz Garcia 1 , F. Ropero Carmona 1 , M. Gonzalez Ruiz 2 , P. Simon Silva 1 , J. Quiros Rivero 1 , Y. Rios Kavadoy 1 , M.C. Cruz Muñoz 1 , J. Cabrera Rodriguez 1 1 Badajoz University Hospital, Radiation Oncology, Badajoz, Spain ; 2 Punta de Europa Hospital, Radiation Oncology, Algeciras, Spain Purpose or Objective Purpose/Objective : obesity is related to worst pronostic factors after prostatectomy and lower prostate cancer specific survival (PCSS) after radiotherapy with low doses of external beam radiation (EBRT). Our objective is to