ESTRO 38 Abstract book

S849 ESTRO 38

prostate cancer, being after MRGB 57% GS6, 26% GS7 and 17% GS8-10. Kendall`s correlation coefficient was 0.8. MRGB gave the diagnosis of the 22 initially negative patients; 2 of them were GS6, 6 GS7, 13 GS8-9; about patients initially GS6, 5 of them were finally GS7 and 2 GS8. Also, it confirmed histological suspicious lesions located on the anterior and transitional zone (considered as higher risk) seen in mpMRI but not in TRUS in 17 patients (11%). Grades GS8-9 were related to stages T3a, T3b and T4 by mpMRI with a Spearman´s correlation coefficient of 0.42. Correlated with PIRADS classification, 16% of GS 6 were PIRADS 2-3, 63% PIRADS-4 and 20% PIRADS-5. Among GS7, 8% were PIRADS2-3, 33% PIRADS-4 and 58% PIRADS-5. Of the GS8-9, 44% were PIRADS-4 and 56% PIRADS-5. The GS 8-9 values were associated with higher PIRADS, with a Spearman correlation coefficient of 0.287. Regarding the risk group, after mpMRI +/- MRGB, 52% belonged to high risk, to medium risk 27.5% and to low risk 20.5 %, while initially 14% did not have diagnosis, 11% belonged to high risk, 36 % to intermediate and 39% to low risk group. Spearman´s correlation coefficient was 0.5. As a result, mpMRI changed the treatment in 54% patients; 41% left active surveillance, brachytherapy was rejected in 5% and surgery in 8%, being finally treated with radiotherapy plus hormone therapy.

irradiated with combined treatment, first with HDR Brachytherapy = 15 Gy in a single fraction, with Ir- 192, Microselectron v2 Nucletron-Elekta. In that same act, 4 fiducial markers of intra-prostatic titanium were implanted for posterior IGRT. Two weeks later, IMRT+IGRT was performed on 15 fractions of the Novalis Tx linear accelerator (BrainLab-Varian), high resolution multilane collimator (HDMLC) with 2.5 mm wide slices . IGRT (intra and interfraccion) were based on ExacTrac (BrainLab) localization system. The CTscan was performed every 2.5 mm at the prostate level. Drawing volumes and dosimetry planning were performed in the Eclipse (Varian system). Prescribed dose at 95% PTV-prostate + seminal vesicles ans Pelvic Lymph nodes was = 39 Gy. Genitourinary toxicity (GU) was assessed using the IPSS (International Prostate Symptom Score) and gastrointestinal (GI) scale according to the RTOG criteria. The PSA was recorded systematically during the follow-up. Results The mean age was 66.7 years [47.1-76.7]. Average follow- up of 9 months [0.0-37.4]. The mean IPSS pre HDR-B was 7.4 [0-28]. Post IMRT + IGRT = 6.9 [1-25]; 6.4 [1-22] and 5.4 [1-22] for 2; 6 and 12 months respectively. The rate and degree of rectal toxicity after HDR-BQT + IMRT-IGRT was at 2 months G0 = 0%; G1 = 100%; G2 = 5.4% and G3 = 0%; G4 = 0% At 6 months: G0 = 0%; G1 = 100%, G2 = 0%; G3 = 0% and G4 = 0%. At 12 months: G0 = 0%; G1 = 100%; G2 = 0%, G3 = 0% and G4 = 0%. The mean PSA at 6 months was 0.28 ng / ml [0-1.2] and at 12 months 0.15 ng / ml [0-1.1] Conclusion According to the results presented, we didnt see anay moderate or severe urinary nor rectal toxicity. Related to these results, lymph nodes irradiation in a hypofractionation schedule, could be a safe options for patients. Due to the limitations ofthese report, related to low patient volumen and short follow up, tese results should be confirmed in a prospective trial. EP-1572 How multiparametric magnetic resonance changes the staging and treatment of prostate cancer S. Fernandez Alonso 1 , S. Guardado Gonzáles 1 , J. Durá Esteve 1 , A. Rodríguez Antolín 2 , M.J. Buj Pradilla 3 , I. Alda Bravo 1 , M. Alarza Cano 1 , J.F. Pérez-Regadera Gómez 1 , M.Á. Cabeza Rodríguez 1 1 Hospital Universitario 12 de octubre, Radiation Oncology, Madrid, Spain ; 2 Hospital Universitario 12 de Octubre, Urology, Madrid, Spain ; 3 Hospital Universitario 12 de Octubre, Radiodiagnosis, Madrid, Spain Purpose or Objective To determine the implication of mutiparametric magnetic resonance (mpMRI) in the management of localized prostate cancer (PCa) and the correlation between PIRADS A retrospective study and a correlation statistical analysis were carried out in 149 patients diagnosed with localized PCa who underwent mpMRI +/- MR-guided biopsy (MRGB) before receiving treatment between 2015 and 2018. Results The mean age was 66 years and the mean PSA was 10.02 ng/ml. The mean time interval between diagnosis and mpMRI was 14 weeks. The indication for mpMRI was staging in 73% cases, diagnostic in 16% and follow – up in 10%. Rectal examination, transrectal ultrasound (TRUS) and transrectal biopsy did not found disease in 22 cases (14%). In cases where illness was found, 67% were T1c, 21% T2a, 10% T2b-c and 2% T3a. After MpMRI 15% were T1c, 15% T2a, 20% T2b-c and 40% T3-4. Spearman´s correlation coefficient was 0.33. Regarding GS, before MRGB 22 cases had not got histological confirmation; 60% were GS6, 19% GS7 and 7% GS8-10. MpMRI detected more clinically significant and histological grade. Material and Methods

Conclusion Through clinical staging with TRUS and TRUS-guided biopsy, histological grade and staging of a part of tumors may be underestimated In our experience, mpMRI modified histological grade in a third of patients, risk group in 50% and treatment decision in 54% cases. Therefore, we recommend the use of mpMRI in PCa staging to carry out an adequate management of the disease according to its characteristics. EP-1573 Is there an optimal OAR-filling protocol reducing G2+-toxicity for prostate IMRT? J. Marzec 1 , F. Paulsen 1 , S. Westbomke 1 , Z. Outaggarts 1 , D. Wegener 1 , D. Thorwarth 2 , D. Zips 1 , A. Müller 1