Abstract Book

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ESTRO 37

irradiation of the prostate cancer with low risk or intermediate stage. MRI evaluation was realized in sagittal and axial plans with T2 slides of 2,5 mm thickness. Results 16 pts were implanted with the balloon, 19 pts with the AH gel and 11 with PEG gel. Hydro-dissection was performed in every procedure before implant. MRI exams were assessed between 1 week and one month after implantation. There was no failure of pose. The 3D implanted volume measured, on the MRI ,of physiological salt solution withinthe balloon or gel was 13,5 cc on average, variable according to the technique (12.21 cc balloon, 14,69 cc AH gel and 12 cc PEG gel). Analysis of the anterio-posterior distance generated between prostate gland and rectum following implant was conducted at 3 levels (base, mid gland and apex) : mean distance was 14,2 mm, 11,3 mm et 10 mm with the 3 spacers respectively. With BB mean distances were 16,3 mmat the base, 12,1 mm at mid gland and 8,9 mm at apex. For AH and PEG gels, same measures were 11,97 mm and 14,94 mm at the base, 9,4 mm and 13,18 mm at mid gland and 10,37 mm and12,34 mm at apex respectively. In this study BB showed a better space volume created after implant whereas better distance at apex was assessed with gels than balloon, with statistical significance. As a result of good conditions of implantation there was no noteworthy toxicity in this study. Leakage of gel on péri rectal laterallly was noticed for 4 pts with AH du to specific implant procedure (use of 3 needles with AH instead of one with PEG). For EBRT treatment with IGRT using CBCT, BB was easier for patient repositioning than gels (less visible on CBCT). Conclusion This MRI study confirms the opportunity of creating a good space between prostate gland and rectum whatever system used, with a excellent implantation profile. Nevertheless differencies exist between these 3 spacers in terms of operating implantation, size of space generated post implantation and IGRT conditions for EBRT for prostate cancer treatment. A learning curve is necessary for each system. EP-1601 PET imaging in patients with biochemical progression treated with high dose salvage radiotherapy R.M. D'Angelillo 1 , L.E. Trodella 1 , M. Fiore 1 , A. Iurato 1 , A. Carnevale 1 , C. Greco 1 , A. Sicilia 1 , M. Miele 1 , P. Trecca 1 , L. Trodella 1 , S. Ramella 1 1 Campus Biomedico University, Department of Radiation Oncology, Roma, Italy Purpose or Objective Biochemical recurrence after radical prostatectomy occurs in 15-50% of operated patients. Site of recurrence is generally unknown, and radiotherapy is generally adopted as salvage treatment with 60-66 Gy delivered to prostatic fossa. Dynamic 18F-Choline PET/CT could identify biological target volume (BTV), thus to ameliorate radiotherapy target definition and results. Material and Methods Data on 155 patients with biochemical progression after radical prostatectomy between January 2009 and December 2015 were reviewed. All patients at time of diagnosis of biochemical recurrence underwent to dynamic 18F-Choline PET/CT, which revealed in all cases a local recurrence. High-dose salvage radiotherapy (HD- SRT) was accordingly delivered up to total dose of 80 Gy

to BTV. Toxicity was recorded according to CTC vers. 4.0 scale. Results The mean value of PSA before radiotherapy was 1.21 ng/ml. Treatment was generally well tolerated: 143 patients (92%) completed treatment without any interruption. Acute toxicity was: Gastro-intestinal (GI) in 62 patients (40%); Genito-urinary (GU) in 31 patients (20%). No grade > 3 acute toxicity was recorded. Late toxicity was: 16 events (10.3%) of grade 1 GU toxicity and 9 patients (5.8 %) with grade 1 GI. Three patients (1.9 %) experienced grade 2 toxicity (two gastro-intestinal and one genito-urinary toxicity). With a mean follow-up of 48 months 38/155 (24.5%) experienced a biochemical Dynamic 18F-Choline PET/CT could identify BTV in biochemical relapsed patients. HD-SRT delivered according to PET/CT data is safe and could validate ex- adiuvantibus the role of functional data overcoming the definition of biochemical recurrence. EP-1602 MPMRI planning in salvage radiotherapy of biochemical recurrence after radical prostatectomy S. Vukcaj 1 , G. Perugini 2 , R. Muni 1 , E. Iannacone 1 , S. Takanen 1 , F. Piccoli 1 , F. Filippone 1 , L. Maffioletti 1 , M. Kalli 1 , L. Feltre 1 , P. Ghirardelli 1 , G. Querques 2 , M. Roscigno 3 , L. Da Pozzo 3 , S. Sironi 2 , L. Cazzaniga 1 1 ASST Papa Giovanni XXIII, Radiotherapy, Bergamo, Italy 2 ASST Papa Giovanni XXIII, Radiology, Bergamo, Italy 3 ASST Papa Giovanni XXIII, Urology, Bergamo, Italy Purpose or Objective To describe how MPMRI can influence treatment decisions, target volumes delineation and dose prescription, in patients (pts) with biochemical recurrence after radical prostatectomy Material and Methods 11 pts with biochemical recurrence (PSA > 0.2 ng/ml or PSADT (Doubling Time) < 6 months) after radical prostatectomy were studied with MPMRI. Based on MPMRI findings we defined two groups of pts. In the first group (6 pts) MPMRI did not show any macroscopic recurrence so salvage radiotherapy (SRT) was delivered on prostate bed according to the standard dose prescription (70Gy/35 frx, homogenously). In the second group (4 pts) MPMRI detected a macroscopic recurrence, defining two different PTVs and dose prescriptions: an High Risk (HR) volume (72 Gy/32 frx) and a Low Risk (LR) volume (64 Gy/32 frx). CTV HR corresponded to macroscopic recurrence and was defined by MPMRI-T2 images fusion with simulation CT, CTV LR was the remaining prostate bed. All treatments were conducted using Volumetric IMRT- Simultaneous Boost technique and daily IGRT. We used Student’s T-Test to compare intersection volume averages: rectum and PTV (HR and Standard), bladder and PTV (HR and Standard). Acute toxicity were assessed every weeks using the RTOG score. recurrence. Conclusion