ESTRO 36 Abstract Book

S713 ESTRO 36 _______________________________________________________________________________________________

established treatment dose specifications and DHV constraints: in particular, for PTV, plans were optimised aiming to obtain V95%>95% D98%>94%, V2%<108%; concerning the rectum, the requirements were: mean<18Gy, V20<35%, V32 <10%, V37<5%,D1%<40Gy while for the bladder, the goal was to keep mean dose <14 Gy and V21 <40%, V33 < 30%, V38 <13%,D1%<40Gy. Routine institutional image-based patient position verification protocols foresaw daily on-line matching by CBCT. The acute and late toxicities were recorded using the RTOG/EORTC scale. Additional data were collected by means of I-PSS e IIEF-5 questionnaires. Biochemical failure was determined using the Phoenix definition. Results The median follow-up duration was 27 months (range: 24 to 36 months). The median age was 74 years (range: 57–80 years). Most dosimetric parameters for the OARs are well within the protocol constraints, with the n otable exception of maximal doses to rectum and bladder (exceeding in about 20% of cases), but we did not find any statistical correlation with late toxicities. Acute GU toxicity of grade 2 (increase in urinary frequency) was observed in 7% patients. The incidence rates of late GI and GU toxicity of any grade were 14.2% and 35.7%, respectively. The late GU toxicity of grade ≥ 2 was 4.7%. No GE late toxicity ≥ 2 was noted. Previous abdominal surgery appeared to be statistically significant (p= 0.004; Fisher’s test) for the increase of probability of late GE toxicity. The 3-year local recurrence-free survival rate was 98%, only one patient had clinical abdominal lymph node failure. Among the dosimetric data, only V21 (mean value: 22.1%; range: 8.5-55.2%) revealed to be statistically significant for the late GU (p= 0.035; Wilcoxon Mann Whitney Test). Conclusion Our experience with VMAT-based SBRT in low-and intermediate–risk prostate cancer demonstrates favorable efficacy in tumor control and toxicity profile with no decrease in QOL as determined by I-PSS, IIEF. The general good quality of the clinical outcome and the results concerning GI and GU toxicities seem to confirm the robustness of the dosimetric paradigm adopted. Longer follow-up is needed to investigate complete safety and efficacy of the stereotactic treatments. EP-1330 Predictive factors for urinary toxicity in patients treated with radical ebrt for prostate cancer C. Pisani 1 , A. Galla 1 , D. Beldì 1 , G. Apicella 1 , G. Loi 2 , M. Krengli 1 1 University Hospital Maggiore della Carità, Radiotherapy, Novara, Italy 2 University Hospital Maggiore della Carità, Medical Physics, Novara, Italy Purpose or Objective Acute and late toxicity scores in patients treated with radical external beam radiotherapy (EBRT) for prostate cancer were correlated with dosimetry and clinical data in order to identify some predictors for urinary (GU) toxicity. Material and Methods This study enrolled 280 patients (pts) treated with EBRT as primary treatment for prostate cancer in our University Hospital. All patients had at least 24 months follow-up, with a median of 47 months (range: 40-98). According with NCCN risk classification, 18% of pts were at low risk, while the others were at intermediate or high risk. Prescribed dose was 74-78 Gy. Adjuvant androgen deprivation consisting of a luteinizing hormone-releasing hormone analog, was administered in 192 patients (68.6%). All patients completed a pre-EBRT questionnaire, registering baseline GU symptoms and patients’ medical history (diabetes,hypertension, previous surgery, and

smoking) and were assessed by International Prostatic Symptom Score (IPSS). Toxicity was registered following a grading system based on the Radiation Therapy Oncology Group (RTOG). Acute toxicity was defined as toxicity occurring during or within 3 months after the end of EBRT. Late toxicity was defined as toxicity occurring for the first time >3 months after the end of EBRT or as acute toxicity lasting longer than 3 months. Acute and late GU toxicities were correlated with dosimetry and clinical parameters (age , presence of co-morbidities including previous TURP, tumor stage, initial PSA and Gleason Score). Results Median age was 74 years (range: 64-83); performance status according with Karnofsky scale was 90 (80-100). Fifty percent of pts had cardiovascular disease and 13% of them had undergone TURP before EBRT. Thirty-two percent of pts were treated with IMRT and 20% with IGRT. Median bladder volume at simulation was 263 cc. Thirty- one percent of pts experienced acute G1 GU toxicity, 24% G2 and 3% G3. No G4 GU acute toxicity was reported. Fourteen percent of pts experienced G1 late toxicity and 3% G2. We did not report any G3 or G4 GU toxicity. IPSS baseline value significantly correlated with acute GU toxicity in univariate (p=0.009) and multivariate (p=0.0002) analysis. The presence of nicturia (p=0.002), bladder urgency (p=0.024) and incontinence (p=0.024) also significantly correlated with GU toxicity. Bladder volume <200 cc at CT-simulation was also associated with toxicity (p=0.014), while maximum dose to bladder was correlated with late toxicity (p=0.014). The use of 3D-EBRT was significantly associated both with increased acute (p=0.032) and late (p=0.03) toxicity. Conclusion In our study pretreatment IPSS, nicturia, urgency and urinary incontinence at diagnosis, bladder volume < 200 cc during CT-simulation, the use of 3D-EBRT and maximum dose to the bladder was predictive for specific moderate– severe acute urinary symptoms. EP-1331 Efficacy and safety of re-irradiation of locally recurrent prostate cancer with FFF-VMAT G.R. D'Agostino 1 , C. Franzese 1 , L. Di Brina 1 , S. Tomatis 1 , C. Iftode 1 , D. Franceschini 1 , E. Clerici 1 , G. Reggiori 1 , A. Tozzi 1 , P. Navarria 1 , M. Scorsetti 1 1 Istituto Clinico Humanitas, Radiotherapy and Radiosurgery, Rozzano Milan, Italy Purpose or Objective Despite considerable advances in technologies, especially with the introduction of IMRT, IGRT, and VMAT, re- treatment of locally recurrent prostate cancer with external beams radiation therapy remains controversial because of fear of major complications or unbearable side effects. In this study we report our experience on re- irradiation in a sample of 17 patients previously irradiated for prostate cancer. Material and Methods Patients affected by prostate cancer and previously submitted to radiotherapy were included in this study, provided that they had an increased PSA, diagnostic for biochemical relapse, and a PET-Choline revealing the presence of a local recurrence of disease. Re-irradiation consisted of a stereotactic treatment delivered by FFF IGRT-VMAT technology in 5 daily fractions. Clinical response was evaluated with PSA and physical examination. Toxicity assessment according to CTCAE (v. 4.01) criteria. During follow-up, PET-Choline was performed in the cases of PSA rising. Results Between November, 2012 and May, 2016, 17 patients (median age 78 years, range 59-82) were submitted to re-irradiation on prostate (n=10, 58.8%),